Thursday, April 30, 2009

Microbial production and biomedical applications of lovastatin

Lovastatin is a potent hypercholesterolemic drug used for lowering blood cholesterol. Lovastatin acts by competitively inhibiting the enzyme, 3-hydroxy-3-methylglutaryl coenzyme A reductase involved in the biosynthesis of cholesterol. Commercially lovastatin is produced by a variety of filamentous fungi including Penicillium species, Monascus ruber and Aspergillus terreus as a secondary metabolite. Production of lovastatin by fermentation decreases the production cost compared to costs of chemical synthesis. In recent years, lovastatin has also been reported as a potential therapeutic agent for the treatment of various types of tumors and also play a tremendous role in the regulation of the inflammatory and immune response, coagulation process, bone turnover, neovascularization, vascular tone, and arterial pressure. This review deals with the structure, biosynthesis, various modes of fermentation and applications of lovastatin.

Keywords: Lovastatin, HMG-CoA reductase, low density lipoprotein (LDL), high density lipoprotein (HDL), fermentation, biomedical application

Lovastatin is an effective inhibitor of the enzyme hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase (mevalonate: NADP1 oxidoreductase, EC that catalyzes the reduction of HMG-CoA to mevalonate during synthesis of cholesterol [1] . When the lactone ring of lovastatin is in its open form, as it would be in the human liver, the structure bears a strong similarity to HMG-CoA. It has been shown that lovastatin and the other monacolins are very specific competitive inhibitors of the reductase [2],[3],[4],[5] , which reduce serum cholesterol levels by blocking cholesterol biosynthesis as shown in the [Figure 1]. An attractive characteristic of these inhibitors is that they selectively reduce levels of low-density-lipoprotein (LDL), the bad lipoproteins. While levels of high-density lipoprotein (HDL, the good lipoproteins) remain unaffected, or in some cases, even increase. Lovastatin is currently made commercial by fermentation. However, other synthetic routes have also been considered. One of the reported routes is by a cell-free extraction in aqueous solution, where the lactone ring is in its open form [6] . Another method involves the use of silyl ethers [7] .

Lovastatin (or mevinolin, monacolin K, and Mevacor, Merck) contains a methylbutyric side chain (R1) and a 6-α methyl group (R2) as shown in [Figure 2]. The foremost query addressed was whether a reduction in plasma cholesterol level with lovastatin would be associated with a reduction in the whole body production rate of cholesterol or with the sizes of exchangeable body cholesterol pools as determined by the three-pool model of cholesterol turnover. The mean plasma cholesterol level decreased 19.4% (from 294 to 237 mg/dl), and low-density lipoprotein cholesterol decreased 23.8 % (from 210 to 159 mg/dl) with lovastatin therapy. Thus, HMG-CoA reductase inhibition by lovastatin at the therapeutic dose used here did not change the steady-state rate of whole-body cholesterol synthesis. Some of the study explained that lovastatin enhanced the healing rate and increased biomechanical properties of the bone at the fracture site. Lovastatin therapies have been shown to reduce cardiovascular events, including myocardial infarction, stroke and death, significantly, by altering vascular atherosclerosis development in patients with or without coronary artery disease symptoms [8],[9] . Through the analysis of the inhibitory effect on HMG-CoA reductase, it is possible to highlight the influence of the obtained structures on biological activity. The stereochemistry of the side chain ester moiety is not important for inhibitory binding to HMG-CoA reductase, as the spatial requirements of the acyl moiety are compatible with compact, branched-chain aliphatic acyl groups, and additional branching at the α carbon of the acyl moiety increases potency.

Various fungi such as Aspergillus ( A. terreus ) species, Monascus ( M. ruber, M. purpureus, M. pilosus, M. vitreus, M. pubigerus and M. anka ) species , Paecilomyces viridis and Pencillium ( P. citrinum ) species have been found to produce lovastatin [7] . Uncontrolled filamentous growth occurs when using rapidly metabolized substrates. The rapid increase in viscosity accompanied by filamentous growth greatly impedes oxygen transfer and this is said to explain the low titers of lovastatin. Fermentation-derived lovastatin is a precursor for simvastatin, a powerful semi-synthetic statin commercially available as Zocor TM . Simvastatin is obtained via a selective enzymatic deacylation of lovastatin [8] . An alternative method for the lovastatin synthesis was semi-synthetic route where the synthesis occurs via the regioselective enzymatic esterification of 2-methylbutyric acid and a diol lactone precursor. The method has the potential advantage that different analogs of lovastatin can be synthesized from the same lactone precursor using different carboxylic acids. Lovastatin also inhibits tumor growth through the inhibition of non-sterol isoprenoid synthesis. Lovastatin (mevinolin) was the first hypocholesterolemic drug to be approved by Food and Drug administration (FDA), USA.

Various Modes of Fermentation Top

Submerged batch fermentation of lovastatin production was reported in various literatures and commercial production of lovastatin is based on A. terreus batch fermentation and most of the literature deals with this species [7] . Aspergillus terreus fermentations were typically carried out at 28º and pH 5.8-6.3. The dissolved oxygen level is controlled at 40% of air saturation. Batch fermentation generally runs for less than 10 days. In some cases, pelleted growth of A. terreus has yielded higher titers of lovastatin than obtained with filamentous growth. The composition of a fermentation medium influences the supply of nutrients and metabolism of cells in a bioreactor and therefore the productivity of a fermentation process depend on the culture medium used. Of the major culture nutrients, carbon and nitrogen sources generally play a dominant role in fermentation productivity because these nutrients are directly linked with the formation of biomass and metabolites [10] . Also, the nature and concentration of the carbon source can regulate secondary metabolism through phenomena such as catabolic repression. Response surface methodology (RSM) was also adapted in identifying the impact of the medium composition on lovastatin production with a high producing A. terreus . The effect of concentrations of several carbon and nitrogen sources were studied and a significant interactive effect of the medium constituents on lovastatin titers was observed [11] . The RSM technique was used to optimize the culture medium for producing lovastatin from Monascus rubber [12] . No report exists on any interactive effects of dissolved oxygen and the other nutrients on the production of lovastatin. Process optimization is a tedious process due to involvement of multivariable process parameters. Screening of important factors is initially carried out and the selected factors are then optimized by different techniques. RSM has some advantages that include less experiment numbers, suitability for multiple factor experiments, search for relativity between factors, and finding of the most suitable condition and forecast response [13] . Fed-batch fermentations of A. terreus have been investigated for producing lovastatin and are said to be superior to batch cultures, because of the feed-back inhibition of product to its own synthesis. Submerged fermentation processes for large-scale lovastatin production have been developed using A. terreus and other species [10],[14] . Solid state fermentation uses economical substrates (agricultural residues), requires fewer processing and down-streaming stages, utilizes lesser power and generates lesser effluent. Moreover, SSF has higher product yield and offers better product stability. Because of the reasons, solid state fermentation was used mainly for the production of industrial enzymes but nowadays, it is also being exploited for the production of secondary metabolites. However, there is no discussion in the literature of how the concentration of lovastatin might affect its own synthesis by A. terreus . Product inhibition of fermentation is a crucial influence in many industrial processes, but has not been documented for lovastatin production [14],[15],[16] .

Biotransformation investigations of statins were carried out on 14 C-labelled monacolin J and L, employing a strain of Monascus ruber, suggested that these compounds are precursors of lovastatin and consequently can be classified as isolated intermediate metabolites in the lovastatin biosynthetic pathway [17] . Subsequent experiments employing the cell-free extract of M. ruber and living cells of Paecilomyces viridis have demonstrated the transformation of monacolin J [6] . Moreover, a combination of physical techniques indicates monacolin M derivation from monacolin J, via a pathway that is quite distinct from that for the synthesis of lovastatin, the α-methylbutyryl ester of monacolin J[3] .

Biochemical Pathways in Lovastatin Synthesis Top

From an overview of the early biogenetic studies carried out on the monacolins, it is possible to demonstrate that monacolin L is the first to be synthesized from nine molecules of acetate and is, in turn, converted to monacolin J by hydroxylation; monacolin K is then derived from monacolin J. The monacolin X, i.e., the α-methyl-β-ketobutyryl ester of monacolin J, is converted to lovastatin, while it is accumulated in cultures of mutant strains producing no detectable amounts of lovastatin[3] . The investigation of the biogenesis of lovastatin, carried out mainly in Aspergillus terreus strains employing labeled precursors indicated that the lovastatin biosynthetic pathway starts from acetate units (4- and 8-carbons long) linked to each other in head-to-tail fashion to form two polyketide chains. The methyl group present in some statins in the side chain or at C6 derives from methionine, as frequently occurs in fungal metabolism, and is inserted in the structure before the closure of the rings. Then the main chain is cyclized and in some statins esterified by a side chain at C8. The oxygen atoms present in the main chain are inserted later by aerobic oxidation using a deoxygenated precursor [8],[18] . Studies on the 13 C incorporation in lovastatin carried out with Penicillium citrinum and M. ruber strains indicated a similar pathway; enzymatic hydroxylation and subsequent esterification at C8 was also observed [17].

More-recent investigations have studied the enzymatic kinetics together with gene regulation and expression involved in A. terreus lovastatin biosynthesis. The genetic research investigated the mechanisms involved in lovastatin biosynthesis, particularly with regard to the two polyketide chains. The results, including the characterization of A. terreus lovastatin-blocked mutants, showed that the multifunctional polyketide synthase system (PKSs) comprises a lovastatin nonaketide synthase (LNKS) involved in the cyclization of the main polyketide chain, to form the hexahydro naphthalene ring system, and a diketide synthase (LDKS) involved in the transfer of the methylbutyryl side chain to monacolin J. Study of the primary structure of the PKS that forms the lovastatin nonaketide provided new details of lovastatin biosynthesis. Other aspects of the biosynthesis of lovastatin related to PKSs have been investigated. The LNKS, product of lovB gene, interacts with lovC (a putative enoyl reductase), to catalyze the reactions in the first part of the biosynthetic pathway, leading to dihydromonacolin L. In the final step of the lovastatin pathway, the LDKS, made by lovF , interacts with lovD (transesterase enzyme) that catalyzes the attachment of the 2-methylbutyric acid to monacolin J, derived from monacolin L. Key features of genes encoding these enzymes and regulatory factors in lovastatin production in A. terreus have been elucidated [19],[20].

An intramolecular Diels-Alder endo closure of the hexaketide, to form a bicyclic system, with the same ring stereochemistry as dihydromonacolin L, catalyzed by LNKS purified from A. nidulans was recently demonstrated. Finally in a strain of A. terreus, in which the lovC gene has been disrupted, the post-PKS (post-polyketide synthase) steps involved in the biosynthesis of lovastatin were investigated. The results demonstrated that the role of the lovC protein is to ensure correct assembly of the nonaketide chain in lovastatin by the lovB protein. In contrast, the construction of the methylbutyrate side chain by the LDKS ( lovF protein) does not require lovC protein. The study also demonstrated that the lovC protein has no detectable function in post-PKS processing of dihydromonacolin L. The recent advances in gene cloning have allowed the identification of most of the enzymes involved in lovastatin biosynthesis and have confirmed the biosynthetic pathways hypothesized in earlier investigations [21],[22] . The detailed process of biosynthesis of lovastatin is shown in [Figure 3].

Production of Lovastatin Top

The investigations carried out since 1970s have indicated the possibility of obtaining a wide range of lovastatin as both the final products and intermediates of secondary microbial metabolism, or as products of biotransformation process. Large-scale processes have been developed only for a few of the lovastatin described in the literature. For other molecules research is still ongoing and therefore greatly susceptible to future development. Lovastatin was the first statin to be approved by the Food and Drug Administration, United States (1987) and made available on the pharmaceutical market as an anticholesterolemic drug [23] . However, mevastatin was the first statin discovered. Lovastatin (named mevinolin) was later obtained from a strain isolated from soil and classified as A. terreus at the CIBE Laboratories in Madrid (Spain) [8] and it is also obtained from M. ruber (named monacolin K). A few years later, lovastatin was also obtained from 17 strains of different species of 124 tested strains of the genus Monascus, in particular M. ruber, M. purpureus, M. pilosus, M. vitreus , and M. pubigerus [24] . The genus Monascus, particularly the species M. anka and M. purpureus, is traditionally employed in Asian countries as "red koji" for fermented food (red yeast rice) and beverage production, as well as for red dye. Lovastatin-producing strains are, instead, generally poor producers of red pigments and exhibit an optimum temperature for lovastatin production of around 25°. Lovastatin productivity failed and no increase in red pigments was observed when the temperature range for koji production (30-37°) was employed [24],[25] . Studies on the synthesis and characterization of the lovastatin-related compounds indicated that several monacolins were obtainable, mostly from Monascus strains. Monacolin J and L were isolated and characterized from cultures of an M. ruber strain [3],[4],[26] . In 1985, Endo has reported dihydromonacolin L and monacolin X production and activity from a mutant strain of M. ruber [5] . A series of statins were also obtained by chemical modification of the C8 side chain in the lovastatin molecule and a systematic evaluation of the structure-activity relationships of the obtained compounds was also carried out. One of the obtained molecules, simvastatin was found to be a semi-synthetic molecule with practical applications [27],[28] . Biotransformation studies carried out in the lovastatin to obtain a new and powerful statins [3],[17],[29] .

The industrial process for the production of lovastatin was set up in 1980 using an A. terreus strain (Mevacor, Merck). The process development involved the analysis of different fermentation parameters such as culture homogeneity, effect of various carbon sources, pH, aeration, and agitator design. Producer strain reisolation together with pH control and slow use of the carbon source, in particular glycerol, yielded a fivefold increase (about 200 U/l, arbitrary units) with respect to the initial lovastatin productivity. Scaling-up of the process from an 800 l to a 19,000 l scale revealed that oxygen transfer, related to high viscosity of the fermentation broth, is a serious limiting factor in lovastatin productivity. This limitation was overcome by setting up a more-efficient impeller with increased hydrodynamic thrust and a reduction of power requirement, 66% of that of the Rushton standard turbine [30] .

Metkinen group (The original lovastatin producer) increased the lovastatin production by A. terreus ATCC 20542 strains to reach 7-8 g/l, using mutagenesis procedures and experience acquired in the development program of process improvement. Biocon (Biocon India, Bangalore, India) is one of the companies that have obtained US FDA approval for lovastatin production (January 2001), and patented in June 2001. The company's lovastatin process is based on a proprietary fermentation technology, the Plafractor, a large-scale solid-matrix bioreactor. This new bioreactor has the advantages of solid substrate and submerged fermentation, and allows a reduction of downstream processing problems during product extraction [31] .

The production of biomass and lovastatin by spore-initiated submerged fermentations of Aspergillus terreus ATCC 20542 was studied and shown that the production depends on the age of the spores used for inoculation and the lovastatin titer was found to be 186.5±20.1 mg/l for a spore age of 16 days. The time to sporulation on surface cultures was sensitive to the light exposure history of the fungus and the spore inoculation concentration levels [32] .

The optimized fermentation conditions raised the lovastatin titer by four-fold compared with the worst-case scenario within the range of factors and this study was also investigated that the culture medium had excess carbon but limiting amounts of nitrogen source for the better productivity. This study used statistical analysis in documenting the interactions between oxygen supply and nutrient concentrations in lovastatin production. The Box-Behnken design was used to identify the oxygen content in the gas phase as the principal factor influencing the production of lovastatin. Both a limitation and excess of oxygen reduced lovastatin titers [14] .

In batch fermentation, lovastatin biosynthesis with Aspergillus terreus reached 160 U/l in 161 h at pH 6.8 and a dissolved O 2 tension maintained at 70% and the yield of lovastatin produced in repeated fed batch fermentations was increased by 37% though this took over twice as long as in the batch fermentation. Accumulation of lovastatin suppresses its own synthesis in the microfungus Aspergillus terreus through a feed back regulatory mechanism and hence the product was removed continuously from the production medium. Submerged cultivation of a high yielding strain of Aspergillus terreus DRCC 122 for the production of lovastatin in the batch process has limited success with a maximum titre of 1270 mg/l in 288 h and an overall volumetric productivity of 4.41 mg/l h in a 1000 l bioreactor. A cost effective repeated fed-batch process with maltodextrin and corn steep liquor feed as carbon and nitrogen sources, respectively, showed a significant increase in lovastatin yield. The final titre was 2200 mg/l in 288 h of fermentation, with overall volumetric productivity of 7.64 mg/l h, showing an increase of 73% over the batch process. The maximum specific oxygen uptake rate ( Q O 2 ) and volumetric mass transfer coefficient (K L a) were 0.24 m mole O 2 per g dry cell wt. per h and 280 per h, respectively, in fed- batch process. Homogenity and stability of high producing strain of Aspergillus terreus , the rate of utilization of the carbon source, pH control and high level of dissolved O 2 tension (DOT) are of essential importance for high lovastatin production. In carbon source, the glycerol improved lovastatin production by 30% than the glucose [10],[33] .

Among several organic and inorganic defined nitrogen sources metabolized by A. terreus , glutamate and histidine gave the highest lovastatin biosynthesis level. For cultures on glucose and glutamate, lovastatin synthesis initiated when glucose consumption leveled off. When A. terreus was grown on lactose, lovastatin production initiated in the presence of residual lactose. Experimental results showed that carbon source starvation is required in addition to relief of glucose repression, while glutamate did not repress biosynthesis [12] .

A lovastatin-hyperproducing culture of Aspergillus terreus has shown to produce several co-metabolites extracted from whole broth. The predominant co-metabolite was the benzophenone, sulochrin, reported to arise from a polyketide biosynthetic pathway. This compound was targeted for suppression by classical mutagenesis and screening and this gives raise to increased production of lovastatin than its co-metabolites [34] . Five nutritional parameters were screened using Plackett-Burman experimental design and were optimized by Box-Behnken factorial design of response surface methodology for lovastatin production in shake flask cultures by M. purpureus MTCC 369. Maximum lovastatin production of 351 mg/l were predicted in medium containing 29.59 g/l dextrose, 3.86 g/l NH 4 Cl, 1.73 g/l KH 2 PO 4 , 0.86 g/l MgSO 4·7H 2 O, and 0.19 g/l MnSO 4·H 2 O using response surface methodology [12] .

The production of lovastatin and microbial biomass by Aspergillus terreus ATCC 20542, were studied and the production was influenced by the type of the carbon source (lactose, glycerol, and fructose) and the nitrogen source (yeast extract, corn steep liquor and soybean meal) used and the C:N mass ratio in the medium. Use of a slowly metabolized carbon source (lactose) in combination with either soybean meal or yeast extract under N -limited conditions gave the highest titers and specific productivity (0.1 mg/g h) of lovastatin. The maximum value of the lovastatin yield coefficient on biomass was 30 mg/g using the lactose/soybean meal and lactose/yeast extract media. The optimal initial C: N mass ratio for attaining high productivity of lovastatin was 40. The behavior of the fermentation was not affected by the method of inoculation (fungal spores or hyphae) used, but the use of spores gave a more consistent inoculum in the different runs [11] .

Product quality and high yields of secondary metabolites are the main goals for the commercial success of a fermentation process. A novel approach based on the decision-tree algorithm to determine the key variables correlated with the process outcome and on DOSY-NMR to identify both co-metabolites and impurities was used which improves fermentation systems and speeds up bioprocess development. The approach has been validated in the case of lovastatin production from Aspergillus terreus and showed that the NMR spectroscopy increased speed and productivity of a fermentation process by reducing large scale verification experiments and cost of purification steps; moreover, this approach allows to monitor and guarantee the product chemical validation suitable for pharmacological uses [35] .

A two-stage feeding strategy was shown to improve the rate of production of lovastatin by more than 50% when compared with conventional batch fermentation by Aspergillus terreus . The feeding strategy consisted of an initial batch/fed-batch phase and a semi-continuous culture dilution phase with retention of pelleted biomass in a slurry bubble column reactor. The batch phase served only to build up the biomass for producing lovastatin, a secondary metabolite that inhibits its own synthesis in the producing microfungus. The semi-continuous dilution phase provided nutrients to sustain the fungus, but prevented biomass growth by limiting the supply of essential nitrogen. The preferred pelleted growth morphology that favors lovastatin synthesis was readily obtained and maintained in the bubble column reactor. In contrast, stirred tank fermentation had a substantially lower production of lovastatin because mechanical agitation damaged the fungal pellets [36] .

Biomedical Applications of Lovastatin Top

Coronary Heart Disease (CHD):

Statins are the treatment of choice for the management of hypercholesterolaemia because of their proven efficacy and safety profile and they can exert antiatherosclerotic effects independently of their hypolipidemic action. Since the lovastatin metabolism generated a series of isoprenoids vital for different cellular functions, from cholesterol synthesis to the control of cell growth and differentiation, HMG-CoA reductase inhibition has beneficial pleiotropic effects [37] . Consequently, lovastatin reduce significantly the incidence of coronary events, both in primary and secondary prevention, being the most efficient hypolipidemic compounds that have reduced the rate of mortality in coronary patients. Lovastatin also have an increasing role in managing cardiovascular risk in patients with relatively normal levels of plasma cholesterol. Large-scale clinical trials have demonstrated that the statins substantially reduce cardiovascular-related morbidity and mortality in patients with and without existing CHD. Observational studies have demonstrated an increased risk of ischemic stroke at high cholesterol levels and an increased risk of haemorrhagic stroke at low cholesterol levels. It is suggested that low cholesterol may predispose to haemorrhagic stroke by contributing to a weakening of the endothelium of small cerebral arteries. Many statin trials have focused on coronary events and total mortality. Lovastatin basically improves the endothelial function, modulates inflammatory responses, maintain plaque stability and prevent thrombus formation, with which all sorts artery related diseases could be cured and it has been suggested that the consequence of the shrinkage of the lipid core of the atherosclerotic plaque, avoiding plaque rupture that would otherwise trigger intramural hemorrhage and intraluminal thrombosis [38],[39] .

Cholesterol Lowering Actions:

Cholesterol is generally synthesized in the liver, and statins work primarily by inhibiting an enzyme involved in its synthesis a complex. 3-hydroxy-3-methyglutaryl coenzyme A is converted into mevalonate, a precursor of cholesterol, in the presence of the enzyme HMG CoA reductase [8] . Lovastatin is the hydrophobic ring structure that was covalently linked to the substrate analogue which involved in binding to the reductase enzyme and inhibiting the cholesterol synthesis. This rate-limiting step in cholesterol biosynthesis is blocked by statins. This also reduce the LDL level which cause arthrosclerosis and increase the level of HDL which acts as good cholesterol and it avoids the lesion formation in the artery that leads to narrow down the blood circulation through the arteries but the mechanism was unknown [9] .

Drugs for Alzheimer's Disease (AD):

Lovastatin treatment was observed to reduce the prevalence of AD in patients suffering from hypercholesterolaemia. Many of the known risk factors for AD were associated with cholesterol metabolism. Interestingly, it seems as if higher doses of lovastatin, that is inhibitors of the cholesterol biosynthesis by blocking formation of mevalonate, might lower the progression of AD. The mechanisms, however, by which lovastatin or cholesterol levels exert their influence are unknown. The alternative processing of the amyloid-precursor protein (APP) in the brain of AD patients leads to the production of the neurotoxic amyloid-beta protein (Ab), a causative factor for AD pathology [40] . These findings led to prospective clinical trials of cholesterol-lowering statins in AD patients, even if many studies do not support elevated cholesterol levels in serum and brain as a risk factor for Alzheimer's disease. Thus, upto date there is insufficient evidence to suggest the use of lovastatin for treatment in patients with AD. Several studies demonstrated that the cleavage of APP can be modulated by altering membrane cholesterol levels in vitro [41] .

Lovastatin in Renal Disease Treatment:

The important advances have been used in the treatment of patients with progressive renal disease. The inhibitors of HMG-CoA reductase can provide protection against kidney diseases characterized by inflammation and/or enhanced proliferation of epithelial cells occurring in rapidly progressive glomerulonephritis, or by increased proliferation of mesangial cells occurring in IgA nephropathy. The mechanisms underlying the action of statins are not yet well understood, although recent data in the literature indicate that they can directly affect the proliferation/apoptosis balance, the down regulation of inflammatory chemokines, and the cytogenic messages mediated by the GTPases Ras superfamily. Lovastatin may directly influence intracellular signaling pathways involved in the prenylation of low molecular weight proteins that play a crucial role in cell signal transduction and cell activation. As far as kidney diseases are concerned, lovastatin therapy has been shown to prevent creatinine clearance decline and to slow renal function loss, particularly in case of proteinuria, and its favorable effect may depend only partially on the attenuation of hyperlipidemia [42] .

Lovastatin and Cancer:

In primary cultures of human glioblastoma cells, inhibition of Ras farnesylation by lovastatin is associated with reduction of proliferation and migration. So the proliferations of the cancer cells were inhibited by lovastatin. However, the inhibition of cell growth by lovastatin may be independent of Ras function. In C6 glioma cells treated with lovastatin, free geranylgeraniol overcomes the arrest of cell proliferation, whereas the rescue effect was significantly lower with farnesol. Two recent case control studies, involving over 10,000 individuals, have looked for changes in the rates of cancer at specific sites, but failed to demonstrate a clear association with statin use [43],[44] .

Lovastatin Used in Bone Fraction Treatment:

One of the recent trends is that the treatment of bone fracture is by lovastatin [16] . Lovastatin stimulate bone formation in vitro and in vivo and, when given in large doses or by prolonged infusions, stimulate biomechanical strength of murine long bones with healing fractures. However, administration of lovastatin by large oral doses or prolonged infusions to a fracture site is not a feasible therapeutic approach to hasten healing of human fractures. Lovastatin in biodegradable polymer nanobeads of poly (lactic-co-glycolide acid) to determine if lovastatin delivered in low doses in nanoparticles of a therapeutically acceptable scaffold could increase rates of healing in a standard preclinical model of femoral fracture. Some preclinical studies were suggested that lovastatin administered in a nanobead preparation may be therapeutically useful in hastening repair of human fractures [16] . Garrett et al [16] found that these nanobeads: 1. Stimulated bone formation in vitro at 5 µg/mL, 2. Increased rates of healing in femoral fractures when administered as a single injection into the fracture site, and 3. Decreased cortical fracture gap at 4 weeks as assessed by microcomputed tomography. These preclinical studies were suggested that lovastatin administered in a nanobead preparation may be therapeutically useful in hastening repair of human fractures [16] .

Other Applications:

Lovastatin is also used for the inhibition of the induction of inducible nitric oxide synthase and proinflammatory cytokines in rat astrocytes, microglia and macrophages and to repress MHC-II mediated T-cell activation. Moreover, lovastatin treatment decreased neuroinflammatory activity and clinical signs in experimental allergic encephalomyelitis, an animal model for multiple sclerosis (MS) [45],[46] . In the last few years many studies have demonstrated that statins, in addition to their lipid lowering effects, have antiinflammatory and immunomodulatory properties. These properties of statins have suggested that they could have beneficial effects in immune mediated neurological disorders. Lovastatin therapy can significantly reduce morbidity and mortality in diabetics.

Conclusions Top

Lovastatin inhibit HMG-CoA reductase competitively; decreases LDL level more than other cholesterol-lowering drugs, and lower triglycerides level in hypertriglyceridemic patients. Lovastatin have antiatherosclerotic effects, which correlate positively with the percent decrease in LDL cholesterol. In addition, lovastatin can exert antiatherosclerotic effects independently of their hypolipidemic action. Because the mevalonate metabolism creates a series of vital isoprenoids for different cellular functions, from cholesterol synthesis to the control of cell growth and differentiation, HMG-CoA reductase inhibition has beneficial pleiotropic effects. Lovastatin have become the therapy of interest for the treatment of many dyslipidaemias in the patients with Alzheimer's disease, renal disease treatment, cancer treatment, bone fracture treatment and used as immunosuppressant. Although lovastatin share a common mechanism of action, there are differences in their relative efficacy for improving the lipid profile, as well as in their chemistry and pharmacokinetics. Lovastatin is well tolerated and have an excellent safety record. Consideration of these differences should help to provide a coherent basis for the safe and effective use of the current and budding lovastatin in clinical practice.

References Top

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16. Garrett IR, Gutierrez GE, Rossini G, Nyman J, McCluskey B, Flores A, et al. Locally Delivered Lovastatin Nanoparticles Enhance Fracture Healing in Rats. J Orthop Res 2007;25:1351-7 Back to cited text no. 16 [PUBMED] [FULLTEXT]
17. Endo A, Negishi Y, Iwashita T, Mizukawa K, Hirama M. Biosynthesis of ML-236B (compactin) and monacolin K. J Antibiot (Tokyo) 1985b;38:444-8. Back to cited text no. 17 [PUBMED]
18. Moore RN, Bigam G, Chan JK, Hogg AM, Nakashima TT, Vederas JC. Biosynthesis of the hypocholesterolemic agent mevinolin by Aspergillus terreus : Determination of the origin of carbon, hydrogen, and oxygen atoms by 13 C NMR and mass spectrometry. J Am Chem Soc 1985;107:3694-701. Back to cited text no. 18
19. Hutchinson CR, Kennedy J, Park C, Kendrew S, Auclair K, Vederas JC. Aspects of the biosynthesis of non-aromatic fungal polyketides by iterative polyketide synthases. Antonie van Leeuwenhoek 2000;78:287-95. Back to cited text no. 19
20. Kennedy J, Auclair K, Kendrew SG, Park C, Vederas JC, Hutchinson CR. Modulation of polyketide synthase activity by accessory proteins during lovastatin biosynthesis. Science 1999;284:1368-72. Back to cited text no. 20 [PUBMED] [FULLTEXT]
21. Auclair K, Kennedy J, Hutchinson CR, Vederas JC. Conversion of cyclic nonaketides to lovastatin and compactin by a lovC deficient mutant of Aspergillus terreus . Bioorg Med Chem Lett 2001;11:1527-31. Back to cited text no. 21 [PUBMED] [FULLTEXT]
22. Sutherland A, Auclair K, Vederas JC. Recent advances in the biosynthetic studies of lovastatin. Curr Opin Drug Discov Dev 2001;4:229-36. Back to cited text no. 22
23. Tobert JA. New developments in lipid-lowering therapy: The role of inhibitors of hydroxymethylglutaryl coenzyme A reductase. Circulation 1987;76:534-8. Back to cited text no. 23 [PUBMED] [FULLTEXT]
24. Negishi S, Huang ZC, Hasumi K, Murakawa S, Endo A Productivity of monacolin K (mevinolin) in the genus Monascus . J Ferment Eng 1986;64:509-51. Back to cited text no. 24
25. Juzlova P, Martinkova L, Kren V. Secondary metabolites of the fungus Monascus: A review. J Ind Microbiol 1996;16:163-70. Back to cited text no. 25
26. Endo A, Hasumi K. Dihydromonacolin L and Monacolin X, new metabolites those inhibit cholesterol biosynthesis. J Antibiot (Tokyo) 1985;38:321-7. Back to cited text no. 26
27. Hsu CT, Wang NY, Latimer LH, Sih CJ. Total synthesis of the hypocholesterolemic agent compactin. J Am Chem Soc 1983;105:593-601. Back to cited text no. 27
28. Endo A, Terahara A, Kitano N, Ogiso A, Mitsui S. ML-236B carboxylic acid derivatives and their use as antihyperlipemic agents. US Patent 1979;4,137,322. Back to cited text no. 28
29. Terahara A, Tanaka M. ML-236B derivatives and their preparation. US Patent 1982;4,346,227. Back to cited text no. 29
30. Buckland B, Gbewonyo K, Hallada T, Kaplan L, Masurekar P. Production of lovastatin, an inhibitor of cholesterol accumulation in humans. In: Demain AL, Somkuti GA, Hunter-Cevera, JC, Rossmoore HW, editors. Novel Microbial Products for Medicine and Agriculture. Amsterdam: SIM Publication; 1989. p. 161-9. Back to cited text no. 30
31. Suryanarayan S, Mazumdar K. Solid state fermentation. US Patent 2001;6,197,573. Back to cited text no. 31
32. Porcel ER, Lopez JL, Ferron MA, Perez JA, Sanchez JL, Chisti Y. Effects of the sporulation conditions on the lovastatin production by Aspergillus terreus . Bioprocess Biosyst Eng 2006;29:1-5. Back to cited text no. 32
33. Novak N, Gerdin S, Berovic M. Increased lovastatin formation by Aspergillus terreus using repeated fed-batch process. Biotechnol Lett 1997;19:947-8. Back to cited text no. 33
34. Vinci VA, Hoerner TD, Coffman AD, Schimmel TG , Dabora RL, Kirpekar AC, et al. Mutants of a lovastatin-hyperproducing Aspergillus terreus deficient in the production of sulochrin. J Ind Micro 1991;8:113-20. Back to cited text no. 34
35. Bradamante S, Barenghi L, Beretta G, Bonfa M, Rollini M, Manzoni M. Production of lovastatin examined by an integrated approach based on chemometrics and DOSY-NMR. Biotechnol Bioeng 2002;80:589-93. Back to cited text no. 35
36. Porcel EM, Casas Lopez JL, Sanchez Perez JA, Chisti Y. Enhanced production of lovastatin in a bubble column by Aspergillus terreus using a two-stage feeding strategy. J Chem Technol Biotechnol 2007;82:58-64. Back to cited text no. 36
37. Gibbons RJ, Abrams J, Chatterjee K, Daley J, Deedwania PC, Douglas JS, et al. ACC/ AHA 2002 guideline update for the management of patients with chronic stable angina - summary article: A report of the American College of Cardiology/ American Heart Association Task Force on practice guidelines. J Am Coll Cardiol 2003;41:159-68. Back to cited text no. 37 [PUBMED] [FULLTEXT]
38. Palmer RH, Dell RB, Goodman DW. Lack of effect of lovastatin therapy on the parameters of whole-body cholesterol metabolism. J Clin Invest 1990;86:801-8. Back to cited text no. 38
39. Pickin DM, McCabe CJ, Ramsay LE, Payne N, Haq IU, Yeo WW, et al. Cost effectiveness of HMG-CoA reductase inhibitor (statin) treatment related to the risk of coronary heart disease and cost of drug treatment. Heart 1999;82:325-32. Back to cited text no. 39 [PUBMED] [FULLTEXT]
40. Ohm TG, Meske V. Cholesterol, statins and tau. Acta Neurol Scand 2006;114:93-101. Back to cited text no. 40
41. Eckert GP, Wood WG, Muller WE. Statins: Drugs for Alzheimer's disease? J Neural Transm 2005;112:1057-71. Back to cited text no. 41
42. Buemi M, Senatore M, Corica F, Aloisi C, Romeo A, Cavallaro E, et al. Statins and progressive renal disease. Med Res Rev 2002;22:76-84. Back to cited text no. 42 [PUBMED] [FULLTEXT]
43. Crick DC, Andres DA, Danesi R, Macchia M, Waechter CJ. Geranylgeraniol overcomes the block of cell proliferation by lovastatin in C6 glioma cells. J Neurochem 1998;70:2397-405. Back to cited text no. 43 [PUBMED] [FULLTEXT]
44. Xia, Z, Tan MM, Wong WW, Dimitroulakos J, Minden MD, Penn LZ. Blocking protein geranylgeranylation is essential for lovastatin-induced apoptosis of human acute myeloid leukemia cells. Leukemia (Baltimore) 2001;15:1398-407. Back to cited text no. 44
45. Pahan K, Sheikh FG, Namboodiri AMS, Singh I. Lovastatin and phenylacetate inhibit the reduction of nitric oxide synthase and cytokines in rat primary astrocytes, microglia and macrophages. J Clin Invest 1997;100:2671-9. Back to cited text no. 45
46. Youssef S, Stuve O, Patarroyo JC, Ruiz PJ, Radosevich JL, Hur EM, et al. The HMG-CoA reductase inhibitor, atorvastatin, promotes a Th2 bias and reverses paralysis in central nervous system autoimmune disease. Nature 2002;420:78-84. Back to cited text no. 46

Current status of the regulation for medical devices

In the light of escalating use of medical devices, stringent regulatory standards are required to ensure that the devices are safe, well studied and have least adverse reactions. Recently introduced guidelines and the amendment in the law will provide adequate guidance for both the manufacturers and competent authorities to manage cases efficiently and appropriately. India has emerged as one of the leaders in pharmaceutical industry. Like many other amendments in Drugs and Cosmetics Act that have boosted the global confidence in pharmaceutical industry in India, guidelines for devices will encourage the much needed research in medical devices. Pharmacy personnel can certainly play an important role in the regulation of medical devices. Safety, risks, effectiveness and performance of the medial devices need to be well established and regulated properly. It is hoped that the guidelines are implemented and regulated properly with effective outcome.

Keywords: Drugs and cosmetics act, medical devices, regulations, role of pharmacists

How to cite this article:
Shah AR, Goyal RK. Current status of the regulation for medical devices. Indian J Pharm Sci 2008;70:695-700

How to cite this URL:
Shah AR, Goyal RK. Current status of the regulation for medical devices. Indian J Pharm Sci [serial online] 2008 [cited 2009 Apr 30];70:695-700. Available from:

On October 6, 2005, the Government of India released the Gazette indicating sterile devices as drugs (F. No. 11014/2/2005-DMS and PFA; Gazette No. 1077 dated October 6, 2005) under the sub-clause (iv) of clause (b) of section 3 of Drugs and Cosmetics Act 1940 (23 of 1946) [1] . Earlier as per the sub-clause (iv) of the clause (b) of section 3 of Drugs and Cosmetics Act 1940 (23 of 1946) the definition of drugs included the items "such devices intended for internal or external use in the diagnosis, treatment, mitigation or prevention of disease or disorder in human beings or animals" as may be specified from time to time by the Central Government by notification in the Official Gazette, after consultation with the Board [2] . With this notification various items have been specified as drugs, as given in [Table 1].

It has been further notified vide GSR 127 (E) dated 7/10/2005 that the control over manufacture of these devices would be exercised by CLAA i.e. DCG (I) under the provisions of sub-rule (1) of rule 68A of part VII of the Drugs and Cosmetics Rule, 1945. These rules have been approved by the Ministry of Health and Family welfare and the guidelines issued came in force from March 1, 2006. Some of the highlights of these guidelines are given in [Table 1].

Significance of Medical Devices:

The era of newer development and technology has decreased the morbidity and mortality of life. The medical development in terms of drugs and devices has brought about the robust change in the life of the people (as offered by the cosmetic treatment, dentist, face and cardiology devices). Medical devices have extended the ability of physicians to diagnose and treat diseases, making great contributions to health and quality of life.

According to World Health Organization (Geneva), under Medical Device Regulations, the term "medical devices" includes everything from highly sophisticated computerized medical equipment down to simple wooden tongue depressors. The intended primary mode of action of a medical device on the human body, in contrast with that of medicinal products, is not metabolic, immunological or pharmacological. Medical devices include a wide range of products such as medical gloves, bandages, syringes, condoms, contact lenses, disinfectants, X-ray equipment, surgical lasers, pacemakers, dialysis equipment, baby incubators and heart valves. Medical device means any instrument, apparatus, implant, machine, appliance, implant, in vitro reagent or calibrator, software, material or other similar or related articles, intended by the manufacturer to be used, alone or in combination, for human beings for one or more of the specific purposes like diagnosis, prevention, monitoring, treatment or alleviation of disease; diagnosis, monitoring, treatment, alleviation of or compensation for an injury; investigation, replacement, modification or support of the anatomy or of a physiological process; supporting or sustaining life; control of conception; disinfection of medical devices and providing information for medical purposes by means of in vitro examination of specimens derived from the human body and does not achieve its primary intended action in or on the human body by pharmacological, immunological or metabolic means, but may be assisted in its function by such means [3] .

Medical devices are now a pervasive part of modern medical care. They are in many cases associated with quality of care. In some cases, the use of devices has certainly improved quality. In other cases, devices have associated with many problems. The approach to quality of devices has depended largely on regulation. According to global statistics, 85% of the medical devices are manufactured in the USA, in Japan and in European Union countries. That is the reason why it is matter of concerns to the American and European regulation systems [3] .

Like medicines and other health technologies, they are essential for patient care at the bedside, at the rural health clinics or at the large, specialized hospitals. Medical devices also add to the financial burden on the Government health sector. The medical devices market is showing a double-digit growth. The cardiac devices alone are growing at 20 per cent. In India, the growth of the market is estimated to be between 10-15 per cent. There is a clear indication that the penetration levels are higher in the country. This is because of affordability by patients, increased awareness on health care, improved hospital infrastructure and the increased disease patterns [4] .

The public expects that medical devices meet the highest safety standards. Realizing the importance of Pharmacovigilance, Ministry of Health and Family Welfare, Government of India, with WHO funding, initiated a country wide National Pharmacovigilance Program. Central Drugs Standard Control Organization (CDSCO), New Delhi, coordinates the program. The Honorable Minister of Health, Dr. Anbumani Ramadass at New Delhi, officially launched the program on November 23, 2004. CDSCO has established 2 zonal centres, 5 regional centres and 28 peripheral centres all over India [4] .

Classification of Medical Devices from Regulatory View Point:

Medical devices may be classified as per their medical utility or technical design and manufacturing aspects. However, regulatory authorities around the world have classified them based on their safety requirements and standards of quality to be set. Several criteria are considered to evaluate the potential risk: degree of invasiveness, duration of contact, affected body system and local versus systemic effects. The classification of medical devices differs from country to country but the classification in [Table 2] gives a comprehensive view of various classes of medical devices.

In Europe medical devices must comply with the requirements of the Directive, in accordance with the existing European Norms, and with the monographs of the European Pharmacopoeia (for sutures). The European Norms are edited by the European Committee for Normalization. The national bodies of European Committee for Normalization convert these norms into their respective national standards within 6 months following the publication. The regulatory requirement for different classes of medical devices is given in [Table 3] [5] .

According to the Directive 93/42/CEE and the US regulation 21 CFR 820, in the USA, the procedure to obtain an accreditation depends on the classification of the medical device. The marketing of a medical devices is a subject to the FDA controls and unless exempt require "A marketing clearance". [Table 4] gives regulatory requirements in US for medical devices [6] . Australia registers for therapeutic goods in Australia has classified the medical devices into five classes [Table 5]. The placement of in vitro diagnostic medical devices in the new system is still under consideration. All classes are required to demonstrate conformity with safety and performance requirements. Class IIa, IIb, III and Active implantable medical devices (AIMD) require quality systems verification. Class III devices and AIMDs are subject to the most extensive pre-market assessments [7] .

Regulation of Devices:

The approach to quality of devices depends largely on regulation. In addition, there are many problems in the interface between the machine and the user or the patient that are largely untouched by device regulation, and are considered in quality assurance programs. As essential as device regulation is, it is not sufficient to assure quality. Education is particularly important in this area. Quality assurance programs need to be familiar with common problems with medical devices and how to approach them.

The regulation of medical devices is a vast and rapidly evolving field that is often complicated by legal technicalities. For example, legal terms and their meanings are sometimes non-uniform even within one regulatory system. Optimum safety and performance require among all involved in the life span of a medical device: the government, the manufacturer, the importer/vendor, the user and the public each has a specific role to play in this risk management.

Regulation of Medical Devices in Some Countries:

The regulations (or standards, or norms) are intended to protect the user against the risks associated with design, manufacture and packaging of medical devices. They differ from one country to another.

As a science-based regulatory agency, the US Food and Drug Administration (FDA), is responsible for a large and diverse array of products. Since 1976, that responsibility has included insuring the safety and effectiveness of medical devices. The universe of these medical devices is immense, including approximately 5,000 different types of products encompassing a spectrum of technologies from microelectronics to microbiology. FDA's Center for Devices and Radiological Health (CDRH) regularly monitors trends that point toward future product development. The manufacture and quality assurance of medical devices in USA is subject to the regulation 21 CFR 820 (or Quality System Regulation) and its audit reports are publicly accessible. This regulation came into force in 1978 (20 years earlier than the EU Directive). The US FDA registers the product and authorizes the manufacturer to market it in USA. All the technical monographs published by the profession (associations of manufacturers), as well as the profession's practices have legal force. The US FDA is a single body is being imposed by the national authorities. The inspections are led by sworn inspectors. The competence level is very high. Sanctions are possible in case of non-compliance to the regulation [6],[8],[9],[10],[11],[12],[13] .

The Australian medical devices industry plays an important role in Australia's health sector. Australia is among the world leaders in ensuring high standard international regulation and is one of the five members of the Global Harmonization Task Force (GHTF) for medical devices along with the US, Canada, the European Union and Japan. The GHTF publishes guidelines on basic regulatory practices, but there is nothing concerning the application of these guidelines and no proper inspection is carried out [3] . In Europe three laws, referred to as directives, directive 93/42/EEC: medical devices; directive 90/385/EEC: active implantable medical devices; and directive 98/79/EEC: in vitro diagnostic medical devices are in force in the European Union countries. Only the 93/42/EEC directive concerns the medical equipment which came into effect on June 14, 1998 although the project was published on June 14, 1993. The manufacturers have to meet the requirements of this directive to get the CE marking on a medical device. This marking is mandatory for the marketing and the free circulation of the medical devices in the EU countries without additional control or administrative procedure. This directive also applies to subcontractors. The laws enforcement (Directive 93/42/EEC) is controlled by national bodies or notified bodies whose audits reports are publicly assessable [5] .

The new ISO 13485 (2003) standard, specific to medical devices, replaces the ISO 9001 (2000) generic standard. They contain technical specifications or other precise criteria, which have to be used coherently as rules, guidelines or definitions to ensure that materials, products, processes and services are fit to their purpose. The standards related to the quality assurance system are grouped in the ISO 9000 family. They are generic standards, i.e. their requirements apply to any company, whatever the manufactured product or the delivered service. The ISO 9001 (2000) standard covers the whole system of activities starting from the conception until the sale of the article. It has become the international reference standard for the quality assurance system of medical devices, and even if it is not mandatory. It gets practically a legal force in Europe. Various bodies are appointed by each member state of the EU (Ministry of Health, Ministry of Industry and so on), which has to inform the European Commission, and the other member state of it. The European Commission publishes the list (regularly updated) of the notified bodies, together with their identification number (4 numbers following the CE marking) and the defined tasks for which they have been notified. To carry out the certification of conformity procedures, the manufacturer may apply to the notified body of his choice in any EU country. In practice, the quality level strongly varies from one notified body to another [14] .

Developing countries usually do not have their own regulations on medical devices, but many of them refer to the European or American normative system, including GHTF to facilitate the sell of their products in Europe and USA. Since medical devices caused some accidents, sometimes fatal, their manufacturing process must comply with the Good Manufacturing Practices (GMP). There is a very strict quality assurance on all aspects of the production of the medical devices in order to protect the patient's health. In 1969 the GMP standards were drawn by the WHO for drugs, in 1976 it included regulation 21 CFR 211 on drugs in the USA, and in 1997 it included the regulation 21 CFR 820 on medical devices in the USA [6] .

In India the major source of pharmaceutical regulations is the Drugs and Cosmetics Act 1940. This legislation applies to the whole of India and for all products whether indigenous or imported. The legislation is enforced by the office of the Drugs Controller General of India (DCGI). However, at the field level, enforcement is done by the individual state Governments through their Food and Drug Control Administration (FDCA). Matters of product approval standards, clinical trials introduction of new drugs, and import license for new drugs are handled by the DCGI. With the help of Indian Council of Medical Research, New Delhi the approvals for setting up manufacturing facilities and obtaining license to sell and stock drugs are provided by the State Government. However, a similarly regulatory body for the Medical Devices rules and regulations is yet to be established properly.

Role of Pharmacist in Regulation on Use of Devices:

India has emerged as one of the leaders in pharmaceutical industry. The Indian Pharma sector is growing exponentially. Its value in 2004 was US$ 6 billion which has increased to US$ 10 billion at the end of year 2006. On the manufacturing side there are 23 000 manufacturers (1.2% in formulation, the rest in bulk drugs), imports are 4% of total size of domestic market value US $ 3 billion, and export is Rs. 30 000 crore (2007-08) [15] . Indian drug prices are among the lowest in the world. India has recently being viewed as a place with great potential for clinical research. The pharmaceutical sector and especially the pharmacists have been playing a lead role in these directions. Medical device sector has so far not been even in the thought process of pharmaceutical sector. Pharmacy graduates or post-graduates are not even aware of aware of various medical devices used in hospitals. There are very few pharmaceutical companies that have taken a lead in medical devices (except syringes, medical gloves, bandages, condoms, contact lens, disinfectants, etc). Pharmacy personnel can certainly play an important role in the regulation of medical devices. Following are the steps needed to play a positive role in the reputation of medical devices though pharmacists [3] .

It is necessary to have proper understanding of medical device safety, risk involved, the degree of invasiveness, duration of contact, the body system affected, and local versus systemic effects. One should weigh the risks against the benefits to the patients compatible with a high level of protection of health and safety so that maximum benefit and minimum risk is ensure when a device is being used by doctor.

Pharmacist should be actively involved in the regulation of effectiveness and performance of medical device. One has to provide clinically effective parameters through the manufacturer which are relative to the medical condition. Clinical effectiveness is a good indicator of device performance, which is closely linked to safety.

Pharmacists should be involved in the documentary of standards containing technical specifications or other precise criteria to be used consistently as rules, guidelines or definitions of characteristics, to ensure that materials, products, process and services are fit for their purpose. One has to ensure that the prescriptive, design, performance, and management specifications meet the standards.

Pharmacists can promote to establish voluntary standards by consensus from all interested parties (the stakeholders). The use of voluntary/consensus standards may be developed by experts with access to the vast resources available in the professional and industrial communities. Conformity to such standards can also be assessed by an accredited third party (such as a notified body in Europe), and thereby improve and update the standards. All these can make medical device standards effective and efficient tools for supporting health care, and provide to the manufacturers have the flexibility to choose appropriate standards or other means to demonstrate compliance with regulatory requirements.

Many countries lack access to high-quality devices and equipments that are appropriate for their specific epidemiological needs. This is particularly true in developing countries, where health technology assessments are rare and where little regulatory controls exist to prevent the import or use of substandard devices. With the vast majority of devices in developing countries being imported and this may increase the risk and need to be considered lives at risk.

Conclusions Top

In the era of newer research and development, technology may have both curse and bless for the lives of human beings. Hence, a proper and stringent rules and regulations need to be put forth in the practice. Different regulatory bodies exist that regulate or monitor the activities undergoing in terms of both socio-economic protection of human beings. Looking to scope and requirement of medical devices, India needs to enter in the global market to manufacture their own devices. Thus, a proper rules and regulations are needed to encourage the efficient growth of device industry.

Rules and Regulations for medical devices are required in India. Since, the world market is seeing the accentuating use of medical devices in varied type of patients and with unique patterns of disease, this will not only give a public safety assurance but also the manufacturer will get a detailed, accurate, long term surveillance of the medical device, generating more information and hints for further improvements. Education is particularly important in this area. Quality assurance programs need to be familiar with common problems with medical devices and how to approach them.

References Top

1. The Gazette of India. Part II, Section 3(i). New Delhi: The Controller of Publication; 2005 Back to cited text no. 1
2. Malik V. The Drugs and Cosmetics Act, 1940. Lucknow: Eastern Book Company; 1940. p. 5. Back to cited text no. 2
3. World Health Organization Medical device regulations: Global overview and guiding principles. Geneva. Available from: [last accessed on 2006 Mar 5]. Back to cited text no. 3
4. Available from: [last accessed on 2006 Mar 5]. Back to cited text no. 4
5. Available from: [last accessed on 2006 Mar 5]. Back to cited text no. 5
6. Available from: [last accessed on 2006 Mar 10]. Back to cited text no. 6
7. Available from: [last accessed on 2006 Mar 8]. Back to cited text no. 7
8. Bronzino JD, editor. The Biomedical Engineering Handbook. 1st ed. Nebraska: CRC Press; 1995. Back to cited text no. 8
9. Bynum WF, Porter R, editors. The companion encyclopedia of the history of medicine. Routledge companion encyclopedias. New York: Cambridge University Press; 1993. Back to cited text no. 9
10. Porter R, editor. Cambridge illustrated history of medicine. New York: Cambridge University Press; 1996. Back to cited text no. 10
11. Steichen, Felicien M, Welter R, editors. Minimally invasive surgery and new technology. 1st ed. Missouri: Quality Medical Publishing; 1994. Back to cited text no. 11
12. Webster JG, editor. Encyclopedia of medical devices and instrumentation. 2nd ed. New York: Wiley; 2006. Back to cited text no. 12
13. Hirschowitz BI, Curtiss LE, Peters CW, Pollard HM. Demonstration of a new gastroscope, the fiberscope. Gastroenterology 1958;35:50-3. Back to cited text no. 13 [PUBMED]
14. Available from: Back to cited text no. 14
15. Vakharia P, editor. Pharma update. Ahmedabad: Prachi Publication; 2006. p. 1. Back to cited text no. 15

Water for Instrument Processing2

Steam quality is a measurement of the amount of moisture in steam. For steam sterilization, there is typically greater than 95 percent steam and less than 5 percent moisture. Steam purity is a measure of the amount of contaminants in steam usually coming from the boiler. Impurities in the steam source may have an adverse effect on patients, equipment and the sterilizer itself. Various contaminants may find their way into the steam source. As well as being an obvious risk to patients, these reactive contaminants in the steam may have a damaging effect on the materials in the load, may cause corrosion and impair the longevity and functionality of the devices to be sterilized. Reactions may occur when contaminants come into contact with the surgical devices either directly or indirectly with materials that will come into contact with the sterilized product.

Recently, AMMI published TIR34:2007, which defines four levels of water quality and in what way reprocessing personnel and water maintenance personnel should collaborate with administrative personnel to implement the water quality initiatives:

Step 1: Assessment of water quality: The potable water from public utilities should be analyzed by water maintenance personnel to determine whether the water requires treatment and if so what kind of treatment.

Step 2: Implementation of water treatment process: Water maintenance personnel with device reprocessing personnel should ensure that water treatment provides the type of water quality needed for medical device reprocessing.

Step 3: Assurance of proper water quality: Water quality for the various stages in medical device reprocessing should be audited so that the proper water quality is used in each area.

Step 4: Ongoing monitoring of water quality: Where applicable, monitoring procedures should be established to ensure that the treated water is of adequate quality for reprocessing.

TIR34:2007 identifies four categories of water quality, which is determined by the medical device to be cleaned and by the disinfection or sterilization process used. Portable water can be used for pre-cleaning and cleaning of critical devices and for rinsing of semi-critical and non-critical devices. High-purity water is required for critical medical devices and recommended for semi-critical devices as well. Portable water is water that comes from the tap and requires no further treatment provided that it meets the characteristics in Table 2.

Surgical instrument cleaning needs high-purity, low-endotoxin water. Conductivity measures total dissolved solids. Elevated dissolved solids can cause “mineral tastes” in drinking water. In addition, water high in dissolved solids can cause problems with industrial equipment, automated washers and boilers. According to the literature, conductivity of the water used for surgical instrument cleaning should be limited to 10uS/cm to a maximum of 30uS/cm. This can be achieved easily with an reverse osmosis system. For example, even though our tap water in New Jersey has a conductivity level of 500 to start, which is extremely high, after using a relatively inexpensive reverse osmosis system the conductively level of tap water can be greatly reduced to below the recommended values.

Water containing calcium or magnesium can form hard water deposits. These deposits become less soluble as temperature increases and can trap spores on instrument surfaces, which can survive steam or gas penetration. Soft water treatment replaces these elements by sodium ion exchange. However, softened water has no effect on conductivity without partial ionic reduction that is why reverse osmosis water treatment is important for surgical instrument cleaning preparation. A defective softener has sodium chloride and resin used in the process, which may be part of the back wash process. Chloride is present in most feed waters. Removal of chloride treated water can be read by a conductivity meter coupled with an automatic dump valve drain; where the feed water is above 120 milligrams per liter ion exchange or reverse osmosis is required. Silica (silicate) is also not removed with water softeners. Reverse osmosis or deionized water is required.

Water softening systems have little control over water purity and downstream protection from chloride corrosion of the hospital washer and surgical instruments. AAMI TIR34:2007 states, “Softened water is water that receives limited treatment (softening) to remove inorganic material from the water. It will not reduce microbial levels, nor will it remove organic material from the water.”

According to TIR34:2007, reverse osmosis has become widely used in medical device water purification systems. The advantage of reverse osmosis water is that it “filters out contaminants to a high of efficiency. Reverse osmosis removes particulate matter, organic molecules and pyrogens that deionized water cannot. It is less corrosive to steel and copper.” It is cheaper to run and maintain than deionized water systems. HTM2030 suggests that reverse osmosis would be the obvious choice as a core treatment technology, given its excellent impurity removal spectrum across ionic, organic and microbiological species.

The numbers, types and species of microorganisms in a water supply and in used cleaning supplies increases every time the cleaning products are re-used. Good housekeeping procedures need to be followed to contain and confine organisms to prevent contamination. The Association for the Advancement of Medical Instrumentation (AAMI) and the Association of periOperative Registered Nurses (AORN) recommend using de-mineralized water in the final cleaning step.

There is special concern when ophthalmic instruments are re-processed. Toxic anterior segment syndrome (TASS) is an acute inflammation of the anterior chamber of the eye following cataract surgery. It has been linked to irritants on the surfaces of intraocular surgical instruments, from detergent residues and from bacilli in water baths of ultrasonic cleaners. For example, potable or softened water in early processing steps may result in unacceptable endotoxin levels. In fact, TIR34:2007 recommends that high purity water be used for the final rinse when re-processing medical devices that contact the blood stream, cerebral-spinal fluid or the anterior chamber of the eye.

Although the AAMI working group found insufficient evidence for using high-purity water for instrument processing for every stage of the decontamination process, using purified water has its advantages. Some healthcare facilities have installed central water treatment facilities for various departments in the hospital. Others have found a cost effective way to install point of use water treatment units in the reprocessing area.

Healthcare professionals as well as the public recognize the importance of water as a universal solvent. Hard water ions and chlorides can affect the outcome of instruments processed in healthcare settings. It is important to understand the importance of water in the cleaning process. Water is required to thoroughly rinse off organic and inorganic contaminants and to remove chemicals including detergent residue from medical devices. In conclusion, each healthcare facility needs to determine how pure their water is and to regularly monitor water quality and steam quality, and take the necessary steps, if required, to obtain greater water purity when processing surgical devices and patient-care items.

Wednesday, April 29, 2009

Water for Instrument Processing

Water can dissolve more substances than any other liquid. It is essentially nonionic or neutral. While alkaline and acid solvents can only remove compounds of the same pH, water — being neutral — can dissolve solutions and compounds of any pH. Water is the body’s way of purifying itself. Our bodies are 73 percent water, and more than 80 percent of our blood and brain are water. In addition, as a solvent, water washes through our kidneys and takes toxins out of our bodies. Simply put without water, we would be poisoned and we would cease to exist.

Water is important in all stages of medical device reprocessing. In fact, water is required for each step in the decontamination process, from soaking to manual or automated cleaning to rinsing, including the final disinfecting rinse. Furthermore, even concentrated instrument cleaners are composed primarily of water, the solvent for all chemicals in the solution.

Water that is safe to drink may not be acceptable for reprocessing or for sterilizing surgical devices. Water quality varies from place to place and according to the season of the year. Most public water systems include additives such as chlorine, dissolved salts and sometimes significant naturally occurring mineral content, and even organic contaminants, bacteria and endotoxins. Depending on water hardness and temperature, fresh water used can lead to the formation of hard water deposits, a layer of lime or scale that is difficult to dissolve. And, corrosion may occur under these deposits. When water evaporates, some substances can remain as visible mineral residues. Furthermore, any procedure requiring water in its operation presents a potential hazard. This is particularly true if water is not continually changed or sinks cleaned after use. Water supports the growth of Gram-negative bacteria. Calcium, magnesium and pH can stain instruments and inactivate disinfectants. That is why distilled, reverse osmosis or deionized water is recommended for use dilution with all concentrated instrument cleaners and approved disinfectants.

Tap water is contaminated with toxic heavy metals, synthetic organic chemicals, chlorine, biological parasites and thousands of other harmful contaminants. According to a research group, “EPA reports show that U.S. water supplies contain over 2,300 cancer causing chemicals.”1 In addition, all the chemicals we use will ultimately show up in our tap water. There is no new water; our planet keeps recycling the same water. Furthermore, water treatment facilities are not designed to remove organic chemicals and toxic heavy metals, like lead.

Water treatment today is similar to practices 100 years ago, as water flows through sand beds to remove visible particles and then bleach or chlorine is added to kill bacteria. Furthermore, even treated water can contribute to the problem. In softened water, the hard water ions are replaced by sodium salts, but this does not reduce the substances in the water and alkalinity can greatly increase as a function of exposure and temperature. When a thermal disinfecting rinse is used as the final rinse, metals such as aluminum might be subject to attack. Deionized water removes charged ions, but has no capacity for removal of non charged ions including bacteria and bacterial endotoxins. Polymeric materials used for instrument processing including plastic trays can absorb endotoxins. DI water treatment requires close monitoring for when its capacity is exceeded the treated water can have dangerously high levels of previously removed contaminants. Ultra filtration or UV may be required after deionized water treatment.

Water can also damage stainless steel instruments. Stainless instruments are susceptible to pitting when there is an increase in the chloride content in the water, when there is an increase in temperature, with decreasing pH values, increased exposure times, insufficient drying and concentration of chloride from dry residues to instrument surfaces after evaporation.

In recent years, there has been growing awareness about the importance of water in the decontamination of surgical devices and the harmful effects of even minute quantities of contaminants on patients. This is of particular concern because certain medical devices may introduce contaminants directly into the body that are normally protected by skin and mucous membranes. Metals, organic compounds, microorganisms and pyrogens can lead to adverse reactions. Furthermore patients are particularly susceptible when surgical instruments bypass the body’s defenses.

Water fulfills a variety of functions in the decontamination process. First, it dissolves cleaners and other treatment agents. It provides both mechanical action as well as transfer of heat to the surface of items to be cleaned. Also, it dissolves soluble dirt and impurities and it flushes away instrument chemistries and soil. In addition, water is the source for steam used to sterilize most surgical devices and patient-care items.

Water quality is an important consideration in the decontamination of surgical instruments. In Europe, HTM 2030 provides guidance on the choice, specification, purchase and validation as well as maintenance of automated washers and provides recommendations for purified water standards and system designs as well as steam quality. The standard states, “The sterilization steam must be free from impurities and should neither impair the sterilization process nor damage the sterilizer or the items to be sterilized.”

The use of feed water or steam containing substances in excess of the stated values in the table below can reduce the service life of the sterilizer and in Europe may also void the manufacturer’s warranty. As a result there are specific tolerances relating to the quality of the boiler feed water as follows:

sterile area specification

Cleaning of compresses air filters. (Shavo-Norgren) Cleaning of DM water storage tank. Setting of vials washing machine. Fixing of filter of down-flow unit and to check working. Adjust manometer oil to zero. If HEPA is removed, check DOS test and air velocity. Keep SS boxes washed with DM water. Fix cleaned DM water filters in respective housings. Check all tubing, if required, changed them. Cleaning of split AC filters.
Get the washing machine cleaned thoroughly. Check connections of steam and DM water line. Clean SS Pall filters, GS filter and in-line. Clean SS pots and lids. Clean distilled water storage tanks and 20 Lt. capacity pressure unit. Keep in the area, plastic containers required to soak the stoppers. Clean membrane holder assembly and refill it. Fix filter of air down-flow unit and check working. If HEPA is removed check DOS test and air velocity. Set manometer oil level upto zero. Check availability of Benzalkonium Chloride & Hydrochloric Acid in washing area.
Clean, dry and connect distilled water storage tank. Check working of thermostatic control. Run distilled water plant for 2-3 hours and discard the collection. Check leakages if any during run of distilled water plant. Check water conductivity. Get chemical analysis of distilled water done. Check rate of distilled water collection per hour. Check cleaned SS Pall filter is fixed to the DM water inlet before running the plant. Check working of autoclave thermograph. Check inkbottle for sufficient quantity of link. If possible, calibrate thermograph. Normal servicing of autoclave is done by vendor. Run autoclave for 30 minutes and observe any leakages through steam valves, door gasket and joint. Check working of dial thermometer. Check fixing and conditions of air in-let filter. Check working of pressure gagues. Clean the autoclave with distilled water and Benzalkonium Chloride solution before operating. Clean carriage of sterilizer chamber with vacuum cleaner and then with distilled water and sponge. Cleaning carriage of sterilizer with diluted Hydrochloric Acid and then with water. DOP test of HEPA filter module and air velocity. Run dry sterilizer empty at 300 ºC for 1 hour to check its heating and cooling functions. Check working of thermograph for temperature and time and working of HEPA filter after heating cycle. Checks working of inter locking system of autoclave and dry sterilizer. Check hot air leakages through door gasket. COMPOUDING ROOM Check working of homogenizer. Replace N2 25 mm filter. Connect N2 line for sparging and filtration. Remove unwanted material from tables in compounding room. Keep back material removed from sterile area. Replace all UV tubes after noting intensity. Provide new sippers for operators. Check working of conveyer & filling machine. Check grease in filing machine. Check all nitrogen, oxygen and LPG gas lines for working and leakages. Check all gas liners are correctly identified. Check the pressure of room and change rooms. Check temperature of filling room. Replace old sponge used for wiping foot soles change room. Calculate air change per hour from velocity of air through each terminal HEPA filters. Open all return air riser dampers. Check working of fumigation switch and plate. Get area cleaned with 0.5 % Aarshol again before starting fumigation. Check working of down-flow unit, portable laminar including DOP test and air velocity. Check working of ampoules filling machine if required. SEALING ROOM
Run machine without vials for few minutes. Observe any abnormal sound. Take trial of 2 ml vials sealing. Lubricate the machine and keep ready for use. Thoroughly wipe and clean vibrator with 70 % IPA.
Keep batch ready in inspection room. Remove labels of the product other than those that are under inspection. Take trial of machine without vials. LABELLING ROOM Keep batch and labels ready for labeling on the first day of the start up. Keep about 3.0 kg. Gum Acacia in container. Remove previously labelled products from area. Check al accessories required for labeling. PACKING ROOM Keep packing materials, batch ready for packing. Check all accessories required for packing. Confirm line clearance before packing start up.
Formaldehyde treatment and double regeneration of DM water plant. Formaldehyde treatment should be given only if viable counts are high. Check DM water free from acid, alkali, formaldehyde traces for pH. Clean SS storage tank used for multicolumn distillation still.

New chemical reaction that could greatly accelerate pharmaceutical production

researchers have a developed a new chemical reaction that could greatly accelerate pharmaceutical production, while also cutting costs and toxic by-products.

The reaction, designed by chemistry Professor Mark Lautens and graduate student Eric Fang, simplifies the creation of the basic molecular framework found in many natural products and popular pharmaceuticals like some cholesterol-lowering drugs. Until now, synthesizing this framework - an indole - was inefficient, requiring six to 10 steps and often producing toxic by-products. "This new method only takes three steps and results in less waste," says Lautens, the NSERC-Merck Frosst Industrial Research Chair in New Medicinal Agents via Catalytic Reactions and AstraZeneca Professor of Organic Synthesis.

Indoles are ring structures containing carbon and nitrogen. In the process, the researchers used a metallic element as a catalyst to form two chemical bonds and create a diverse range of indole-containing compounds. These compounds could then be used to make drugs now on the market or form the basis of new therapeutic drugs.

Lautens says this new molecular-level technique could equal big savings and less environmental impact. "In order to make a hundred kilograms of these best-selling drugs, there are often hundreds of litres of solvent used, not to mention the many purification processes involved. Not only are you speeding up the process, you're also reducing waste and energy used in manufacturing."

A provisional patent was filed by U of T's Innovations Foundation in March. The research was funded by the Natural Sciences and Engineering Research Council of Canada.

Fermentation by Yeast


To observe the effect on fermentation of various factors such as temperature, pH, and concentration of the reactant sugar.


  1. Wear protective goggles throughout the laboratory.

Procedure 1 (Effect of Different Concentrations of Sugar on Fermentation Rate)

  1. Obtain three 125-ml Erlenmeyer flasks and label them 1,2, and 3.

  2. Add to each of the three flasks 2.5 g of yeast, accurately weighed.

  3. Weigh accurately 1.0 g of sugar for flask #2 and 2.5 g of sugar for flask #3.

  4. Prepare 350 ml of distilled water, heated to 37°C. Add 100 ml of the water to each of the three flasks. Swirl the contents gently to mix.

  5. Attach a deflated spherical balloon over the mouth of each flask. Secure the balloon with both a rubber band and masking tape that seals the balloon's opening to the neck of the flask.

  6. Wrap the flasks with insulating material provided by your teacher (alternative is to place in a Styrofoam container or incubator set to 37°C).

  7. After 30 minutes, measure the circumference of each balloon, using a piece of string, a narrow ribbon, or a paper strip that can be marked.

  8. Repeat step # 7 after 60 and 90 minutes from the start of the experiment.

  9. Record the data in a properly labeled data table.

Procedure 2 (Effect of Temperature on Fermentation Rate)

  1. Set up three new flasks labeled 4, 5, and 6.

  2. To each flask, add 2.5 g of sugar and 2.5 g of yeast.

  3. Prepare water for three different temperatures: 5°C, room temperature, and 37°C. Add 100 ml of cold water (5°C) to flask #4, 100 ml of room temperature water to flask #5, and 100 ml of 37°C water to flask #6. Gently swirl the contents of the flask to mix.

  4. Attach a deflated balloon to the mouth of each flask and secure with a rubber band and masking tape.

  5. To maintain the various temperatures of the individual flasks, place each in a water bath of the proper temperature using ice or water of the desired temperature.

  6. After 30 minutes, measure the circumference of each balloon. Repeat the measurements at 60 and 90 minutes.

Procedure 3 (Effect of pH on Fermentation Rate)

  1. Set up three flasks labeled 7, 8, or 9.

  2. To each flask, add 2.5 g of sugar.

  3. Prepare 350 ml of water at a temperature of 37°C. Divide the water into three equal volumes and place in separate 150-ml beakers labeled either 7, 8, or 9.

  4. To establish a pH of 2 in beaker #7, add 3 drops of Universal indicator (or use pH paper to test), then add 0.1 M acetic acid solution, drop by drop from a Beral pipet while stirring until you reach a pH of 2 as indicated by the color of the indicator (or pH paper).

  5. To establish a pH of 6 in beaker #8, add 3 drops of universal indicator (or use pH paper). Then add 0.1M acetic acid solution, drop by drop while stirring, until you reach a pH of 6 as indicated by the color of the solution (or the pH paper).

  6. To establish a pH of 11 in the water of beaker #9, add 3 drops of Universal indicator (or use pH paper), then add solid sodium carbonate, Na2CO3, in small amounts (size of a match head) using a spatula. Stir to dissolve, noting color of solution. Continue to add the sodium carbonate until a pH of 11 is reached.

  7. Add 2.5 g of yeast to each flask.

  8. Check the temperatures of the three different solutions and reheat if necessary before measuring out 100 ml of each solution and adding to the individual flasks.

  9. Swirl the contents of the flasks to mix.

  10. Attach a deflated balloon to each flask and seal with a rubber band and masking tape.

  11. Place the flasks in a water bath or incubator maintained at 37°C.

  12. After 30 minutes, measure the circumference of each balloon. Repeat the measurements at 60 and 90 minutes.

  13. At the end of the experiment, measure the pH again with pH paper or note the color of the universal indicator in the solutions.

Data Analysis

  1. For each variable used, determine from your circumference measurements which variable had the greatest affect on the activity of the yeast. (What gas is responsible for inflating the balloons?)

  2. How would you test for the effect of combining all the variables in one flask? What would be the setup for your control? Would there be more than one control?

  3. What do you predict would happen if the temperature in the flask is increased beyond 37°C? What is special about the temperature of 37°C? Why not 30°C or 40°C?

  4. Was there any change in pH of the solutions as measured with pH paper or the change in the color of the universal indicator. If so, how would you explain such a change?

  5. How could you verify your explanation in #4 through experimentation? What chemical changes are taking place in the fermentation? What new substances are produced? How can you chemically verify their presence? How could you chemically determine if they have an effect on the pH of a solution?

  6. Ethyl alcohol is a product of fermentation. Why do you think the fermentation process cannot produce a concentration of alcohol beyond 12%?

Monday, April 27, 2009

Dynamic Dissolution Testing To Establish In Vitro/In Vivo Correlations for Montelukast Sodium, a Poorly Soluble Drug



The objectives of the study was to develop a dissolution test method that can be used to predict the oral absorption of montelukast sodium, and to establish an in vitro/in vivo correlation (IVIVC) using computer simulations.


Drug solubility was measured in different media. The dissolution behaviour of montelukast sodium 10 mg film coated tablets was studied using the flow-through cell dissolution method following a dynamic pH change protocol, as well as in the USP Apparatus 2. Computer simulations were performed using GastroPlus™. Biorelevant dissolution media (BDM) prepared using bile salts and lecithin in buffers was used as the dissolution media, as well as the USP simulated intestinal fluid (SIF) pH 6.8 and blank FaSSIF pH 6.5. Dissolution tests in the USP Apparatus 2 were performed under a constant pH condition, while the pH range used in the flow through cells was pH 2.0 to 7.5. The in vitro data were used as input functions into GastroPlus™ to simulate the in vivo profiles of the drug.


The solubility of montelukast sodium was low at low pH, but increased as the pH was increased. There was no significant difference in solubility in the pH range of 5.0 to 7.5 in blank buffers, but the drug solubility was higher in biorelevant media compared with the corresponding blank buffers at the same pH. Using the flow through cells, the dissolution rate was fast in simulated gastric fluid containing 0.1% SLS. The dissolution rate slowed down when the medium was changed to FaSSIF pH 6.5 and increased when the medium was changed to FaSSIF medium at pH 7.5. In the USP Apparatus 2, better dissolution was observed in FaSSIF compared with the USP buffers and blank FaSSIF with similar pH values. Dissolution was incomplete with less than 10% of the drug dissolved in the USP-SIF, and was practically non existent in blank FaSSIF pH 6.5. The in vitro results of the dynamic dissolution test were able to predict the clinical data from a bioavailability study best.


Dynamic dissolution testing using the flow through cell seems to be a powerful tool to establish in vitro/in vivo correlations for poorly soluble drugs as input function into GastroPlus.

A Review of Poloxamer 407 Pharmaceutical and Pharmacological Characteristics

Poloxamer 407 copolymer (ethylene oxide and propylene oxide blocks) shows thermoreversible properties, which is of the utmost interest in optimising drug formulation (fluid state at room temperature facilitating administration and gel state above sol–gel transition temperature at body temperature promoting prolonged release of pharmacological agents). Pharmaceutical evaluation consists in determining the rheological behaviour (flow curve or oscillatory studies), sol–gel transition temperature, in vitro drug release using either synthetic or physiological membrane and (bio)adhesion characteristics. Poloxamer 407 formulations led to enhanced solubilisation of poorly water-soluble drugs and prolonged release profile for many galenic applications (e.g., oral, rectal, topical, ophthalmic, nasal and injectable preparations) but did not clearly show any relevant advantages when used alone. Combination with other excipients like Poloxamer 188 or mucoadhesive polymers promotes Poloxamer 407 action by optimising sol–gel transition temperature or increasing bioadhesive properties. Inclusion of liposomes or micro(nano)particles in Poloxamer 407 formulations offers interesting prospects, as well. Besides these promising data, Poloxamer 407 has been held responsible for lipidic profile alteration and possible renal toxicity, which compromises its development for parenteral applications. In addition, new findings have demonstrated immuno-modulation and cytotoxicity-promoting properties of Poloxamer 407 revealing significant pharmacological interest and, hence, human trials are in progress to specify these potential applications.

Viscoelastic Properties of Carbopol 940 Gels and Their Relationships to Piroxicam Diffusion Coefficients in Gel Bases



This study was conducted to determine the effect of formula compositions on viscoelastic properties of piroxicam gels using Carbopol 940 as a gelling agent and to determine the relationships between viscoelastic properties of Carbopol 940 gel bases and diffusion coefficients of piroxicam in gel bases.


Piroxicam gels (1.0% w/w) were prepared by using Carbopol 940 as a gelling agent and varying Carbopol 940 concentrations, glycerin, and sodium chloride contents. The in vitro release of piroxicam from gel bases to the receiving media, isotonic phosphate buffer solution (pH 7.4), were carried out using Franz-modified cell. The piroxicam diffusion coefficients were obtained by Higuchi's equation. Rheological property measurements of gel samples were performed via a cone and plate fluid rheometer. Relationships between viscoelastic properties of gel samples and piroxicam diffusion in gel bases were analyzed by Pearson's test at a p value of less than 0.05.


All piroxicam gels exhibited predominantly elastic solid behavior whose magnitude depended on Carbopol 940 concentration. Preparations containing good solvent exhibited more elastic solid characters. In contrast, the piroxicam gels containing higher sodium chloride contents possessed more viscous fluid behavior. Analyzed by Pearson's test at a p value of less than 0.05, piroxicam diffusion coefficients were directly proportional to loss tangent, but were inversely proportional to storage modulus, loss modulus, complex modulus, and viscosity.


There is a potential for predicting drug diffusion coefficients from their correlations to rheological parameters. This could be beneficial to the formulation design of transdermal drug delivery systems including mucoadhesive drug delivery systems.