1. Reducing and enlarging formulas
Dr. Amani M. Elsayed

2. Objectives
To calculate the needed quantities of ingredients from basic formula.

3. Reducing and enlarging formulas (Cont.)
Official formulas and most other formulas are based on the preparation of 1000 ml or 1000 g of product.
The pharmacist may be called upon to make either a smaller or greater quantity and thus must reduce or enlarge the formula while maintaining the correct proportion of each ingredient.

4. Reducing and enlarging formulas (Cont.)
1) Find the conversion factor
Conversion factor = Total Quantity desired
Total Quantity of the official formula
 The total quantity desired and the total quantity of the official formula must have same units so the units cancel and yield a conversion factor without units.
2) Use conversion factor in the formula
Conversion factor X amount of ingredient in official
formula = Amount of ingredient needed

5. Example
Use the official formula below to calculate how much of each ingredient would be needed to make 240 ml of peppermint spirit
Peppermint Spirit
Peppermint Oil ml
Peppermint Powder g
Alcohol qsad ml

6. Answer 1. Find conversion factor = 240 ml = 0.24 1000 ml
2. Calculate the amount of ingredient needed
Conversion factor
Amount of ingredient in official formula
Amount of ingredient needed
0.24
100
24 ml 10
2.4 g
1000
240 ml

7. Example Factor (F) = Amount desired/ amount of formula
From the following formula, calculate the quantity of each ingredient required to make 240 ml of calamine lotion:
Calamine g
Zinc Oxide g
Glycerin ml
Bentonite magma ml
Lime water (Calcium Hydroxide) to ml
Factor (F) = 240/1000 = 0.24 X
Calamine g g
Zinc Oxide g g
Glycerin ml ml
Bentonite magma ml ml
Lime water to ml to make 240 ml

8. Certified red colour Q.S.
Example
From the following formula, calculate the quantities required to make 5 gallons of a Phenobarbital elixir ??
Phenobarbital g
Orange oil ml
Certified red colour Q.S.
Alcohol ml
Propylene glycol ml
Sorbitol solution ml
Water, to make ml

9. Answer 5 gallons = 128 f-oz x 30 ml x 5 = 19200 ml
Enlarging factor = / = 19.2
Phenobarbital = 4 x = g
Orange oil = x = 4.8 ml
Alcohol = x = ml
Propylene glycol = x = 1920 ml
Sorbitol = 600 x = ml
Water to make ml

10. Formula that specify proportional parts
From the following formula, calculate the quantity of each ingredient required to make 1000 g of the ointment
Coal tar parts
Zinc oxide parts
Hydrophilic ointment parts
Total No. of parts = 65 parts
65 parts g
parts X g
X (coal tar) = 1000*5 = g 65

11. Answer (Cont.) 65 parts 1000 g 10 parts X g
X (Zinc oxide) = 1000*10 = g 65
50 parts X g
X (coal tar) = 1000*50 = g
Check total = 1000 g

12. Quiz
From the following formula, calculate the quantity in grams of each ingredient required to make 5 lb of the powder.
Bismuth subcarbonate parts
Kaolin parts
Magnesium oxide parts
(Hint: lb = 454 g)