Reducing and enlarging formulas Dr. Amani M. Elsayed

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

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.

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

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 100 ml Peppermint Powder 10 g Alcohol qsad 1000 ml

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

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 80 g Zinc Oxide 80 g Glycerin 20 ml Bentonite magma 250 ml Lime water (Calcium Hydroxide) to 1000 ml Factor (F) = 240/1000 = 0.24 X 0.24 Calamine 80 g 19.2 g Zinc Oxide 80 g 19.2 g Glycerin 20 ml 4.8 ml Bentonite magma 250 ml 60 ml Lime water to 1000 ml to make 240 ml

Certified red colour Q.S. Example From the following formula, calculate the quantities required to make 5 gallons of a Phenobarbital elixir ?? Phenobarbital 4 g Orange oil 0.25 ml Certified red colour Q.S. Alcohol 200 ml Propylene glycol 100 ml Sorbitol solution 600 ml Water, to make 1000 ml

Answer 5 gallons = 128 f-oz x 30 ml x 5 = 19200 ml Enlarging factor = 19200 / 1000 = 19.2 Phenobarbital = 4 x 19.2 = 76.8 g Orange oil = 0.25 x 19.2 = 4.8 ml Alcohol = 200 x 19.2 = 3840 ml Propylene glycol = 100 x 19.2 = 1920 ml Sorbitol = 600 x 19.2 = 11520 ml Water to make 19200 ml

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 5 parts Zinc oxide 10 parts Hydrophilic ointment 50 parts Total No. of parts = 65 parts 65 parts 1000 g parts X g X (coal tar) = 1000*5 = 76.92 g 65

Answer (Cont.) 65 parts 1000 g 10 parts X g X (Zinc oxide) = 1000*10 = 153.85 g 65 50 parts X g X (coal tar) = 1000*50 = 769.23 g Check total = 1000 g

Quiz From the following formula, calculate the quantity in grams of each ingredient required to make 5 lb of the powder. Bismuth subcarbonate 8 parts Kaolin 15 parts Magnesium oxide 2 parts (Hint: lb = 454 g)