1. PERCENTAGE PREPARATIONS
Dr. Amani M. Elsayed

2. Objectives
Solve pharmaceutical calculation problems involving percentage strengths

3. PERCENTAGE PREPARATIONS
Percentage means “by the hundred” or “in a hundred.” Percents (%) are just fractions, but fractions with a set denominator of 100.
Example: “50%” means “50 in a hundred” or “50/100” or “1/2”.
Converting percentages to fractions
Write the number preceding the percent sign over 100 and simplify the resulting fraction
Example: 25%=25/100=1/4

4. PERCENTAGE PREPARATIONS
Converting fractions to percentages
Write the fraction in decimal form. (3/4=0.75)
Write the decimal over one. (0.75/1)
Multiply the numerator and denominator by (0.75/1 = 75/100)
Because you already know the “divided by a hundred” is the same as percent you can write 75/100 as 75%.

5. TYPES OF PERCENT
a. W/W percent or Weight/Weight percent is defined as the number of grams in 100 grams of a solid preparation.
(1) Example #1 A 5 percent (w/w) boric acid ointment would contain 5 grams of boric acid in each 100 grams of boric acid ointment.
(2) Example #2:A 3 percent (w/w) vioform powder would contain 3grams of vioform in every 100 grams of the vioform powder.

6. TYPES OF PERCENT
b. W/V of Weight/Volume percent is defined as the number of grams in 100 milliliters of solution.
(1) Example #1:A 10 percent (w/v) potassium chloride (KCL) elixir would contain 10 grams of potassium chloride in every 100 milliliters of KC1 elixir.

7. TYPES OF PERCENT
c. V/V percent or Volume/Volume percent is defined as the number of milliliters in every 100 ml of solution.
(1) Example #1:A 70% (v/v) alcoholic solution would contain 70 milliliters of alcohol in every 100 ml of solution.
(2) Example #2:A 0.5% (v/v) glacial acetic acid solution would contain 0.5 milliliters of glacial acetic acid in each 100 milliliters of solution.

8. Examples
How many grams of dextrose are required to prepare 4000 ml of a 5% solution?
2)How many grams of potassium permanganate should be used in compounding the following prescription? ℞
Potassium permanganate %
Purified water ad ml
Sig. As directed

9. Answers
1) 5g 100 ml X g 4000 ml X = 5 * 4000 = 200 g 100 2) 0.02 g 100 ml X g 250 ml X = 0.02* 250 = 0.05 g

10. Examples
3) How many grams of aminobenzoic acid should be used in preparing 8 fluidounces of a 5% solution in 70% alcohol? 4) What is the percentage strength (w/v) of a solution of urea, if 80 ml contain 12 g?

11. Answers
3) 8 fluidounces = 8 * 30 = 240 ml 5 g 100 ml X g 240 ml X = 5* 240 = ) 12 g 80 ml X g 100 ml X = 12* 100 = 15% 80

12. Examples
5) How many milliliters of a 3% solution can be made from 27 g of ephedrine sulfate?
6) How many milliliters of liquified phenol should be used in compounding the following prescription? ℞
Liquified phenol %
Calamine lotion ad ml
Sig. For external use

13. Answers 5) 3 g 100 ml 27 g X ml X = 27* 100 = 900 ml 3
6) ml ml
X ml ml
X = 2.5* 240 = 6 ml
100

14. Examples
7) In preparing 250 ml of a certain lotion, a pharmacist used 4 ml of liquified phenol. What was the percentage (v/v) of liquified phenol in the lotion?
8) Peppermint spirit contains 10% (v/v) of peppermint oil. What volume of the spirit will contain 75 ml of peppermint oil?

15. Answers
7) 4 ml 250 ml X ml 100 ml X = 4* 100 = 1.6% 250 8) 10 ml 100 ml 75 ml X ml X = 75* 100 = 750 ml 10

16. Examples
9) What is the percentage strength (v/v) of a solution of 800 g of a liquid with specific gravity of in enough water to make 4000 ml? 10) How many grams of phenol should be used to prepare 240 g of a 5% w/w solution in water?

17. Answers
9) Weight/ sp.gr = Volume 800/ = 1000 ml 1000 ml 4000 ml X ml 100 ml X = 1000* 100 = 25% ) 5 g 100 g X g 240 g X = 5* 240 = 12 g 100

18. Examples
11) How many grams of a drug substance are required to make 120 ml of a 20% (w/w) solution having a specific gravity of 1.15? 12) How many grams of a drug substance should be added to 240 ml of water to make a 4% (w/w) solution?

19. Answers 11) Weight of solution = sp. gr. * Volume = 1.15 * 120 = 138 g
20 g g
X g g
X = 20* 138 = g
100
Weight of water = weight of solution- weight of drug
= 100 g – 4 g = 96 g
Weight of water = volume * Density
= 240 * 1 = 240 g
4 g g of water
X g g of water
X = 4* 240 = 10 g 96

20. Bonus Questions
If 5 g of boric acid are added to 100 ml of water, what is the percentage strength (w/w) of the solution?
How many milligrams of hydrocortisone should be used in compounding the following prescription? ℞
Hydrocortisone 1/8 %
Hydrophilic ointment ad g
Sig. Apply

21. Bonus Questions
3) How many grams of benzocaine should be used in compounding the following prescription? ℞ Benzocaine 2% Polyethylene Glycol base ad 2 g Make 24 such suppositories Sig. Insert one as directed

22. Bonus Questions
4) If ibuprofen tablets are permitted to contain not less than 90% and not more than 110% of the labeled amount of ibuprofen, what would be the permissible range in content of the drug, expressed in milligrams, for ibuprofen tablets labeled 200 mg each?

23. Homework
If 1500 g of a solution contain 75 g of a drug substance, what is the percentage strength (w/w) of the solution?
If 1000 ml of a syrup with a specific gravity of contain 850 g of sucrose, what is the percentage strength (w/w)?
What weight of a 5% (w/w) solution can be prepared from 2 g of active ingredient?

24. Homework
4) If a veterinary liniment contain 30% (v/v) of dimethyl sulfoxide, how many milliliters of the liniment can be prepared from 1 lb of dimethylsulfoxide (sp. gr. 1.10)?