REDUCTION AND ENLARGEMENT OF FORMULAS

REDUCTION AND ENLARGEMENT
OF FORMULAS
INTRODUCTION
Most of the preparations made in a
pharmacy are from proven formulas
that have been tested and are listed in
the Pharmacopeia/National Formulary
as official formulas.
These formulas list the amount of each
ingredient needed to make a certain
amount of the preparation.
It is necessary to reduce or enlarge a
formula to satisfy the needs of your
pharmacy.
Sample Problem:
Calculate the amount of each ingredient
needed to make 240 ml of Peppermint
Spirit.
Peppermint Spirit
Peppermint Oil............ 100 ml
Peppermint Powder.........10 g
Alcohol.....qsad.......... 1000 ml
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Copying Formula
100 ml
10 g
1000 ml
Peppermint Oil
Peppermint Powder
Alcohol.....qsad
Rx
For
240 ml
For
1000 ml
e.g. 1
Peppermint Spirit
Reduction of formula
e.g 2
Calculate the amount of each
ingredients needed to produce 100
ml of Codeine Linctus B.P.C.
 Refer to formula in B.P.C, then copy;
 note that in BPC, the final volume is
1000 ml; - reduction of formula
26
Syrup B.P. to 1000 ml
Lemon syrup 200 ml
Distilled water 20 ml
Chloroform spirit 20 ml
Benzoic acid 20 ml
Tartrazine compound 10 ml
solution
Codeine phosphate 3 g
For 100
ml
Rx 1000 ml
27
Syrup B.P. to 1000 ml 100.0 ml
Lemon syrup 200 ml 20.0 ml
Distilled water 20 ml 2.0 ml
Chloroform spirit 20 ml 2.0 ml
Benzoic acid 20 ml 2.0 ml
Tartrazine compound 10 ml 1.0 ml
solution
Codeine phosphate 3 g 0.3 g
For 100
ml
Rx 1000 ml
Note that Codeine phosphate is in
powder form; -
 First dissolve codeine phosphate in water
 Then add in other ingredients
 Finally add syrup B.P to 100 ml (final
volume
29
Enlargement of formulas
Distilled water to 10 ml
Chloroform double strength 5 ml
Peppermint emulsion 0.25 ml
concentrate
Sodium bicarbonate 0.5 g
Light Magnesium Trisilicate 0.5 g
Light Kaolin 2 g
For
250 ml
Rx
Calculation of Concentration
in Percentage
Term percent (%)refers to
 ‘by the hundreds’ or ‘in a hundreds’
 Also can be expressed in ratio
 50% means 50 parts in 100.
 In pharmaceutical; 3 types of
percentage
Weight-in-volume (w/v)
 Volume-in-volume (v/v)
Weight-in-weight (w/w)
32
Definition of Percentage
the number of millimeters of a
constituent in 100 mL of
solution/liquid
preparation.
% v/v
According to USP
the number of grams of a
constituent in
100 g of solution or preparation.
% w/w
the number of grams of a
constituent in 100 ml of
solution/liquid preparation.
% w/v
34
Example of percentage
1 %
 1 part in 100 ml of solution
- 1 grams of solute in sufficient amount
of solvent to produce 100 ml
preparation.
 * note that 1 % is NOT 1 gram of
solute in 100 ml of solvent.
35
Calculation of percentage
1:400  1 x 100 % = 0.25 %
400
1:1000  1 x 100 % = 0.1 %
1000
2:2500  ?
4:10,000  ?
36
Calculation of percentage
w/v
Calculate the amount of Sodium Chloride
needed to produce 1.5 L of Sodium
Chloride 0.9% Solution.
Answer:
0.9% - 0.9 g of NaCl in 100 ml of solution
In 100 ml; contains 0.9 g NaCl
In 1500 ml; contains ? g NaCl
37
Therefore:
In 1500 ml  0.9 g x 1500 ml
100
= 13.5 g
Amount Sodium Chloride needed is 13.5 g
- 13.5 g NaCl to be completely dissolved
in a small part of water, then add the
remaining water up to final volume
(1500 ml)