Unformatted text preview: Percentage/Ratio Strength
PRACTICE PROBLEMS
1. A pharmacist received the following prescription:
Phenobarbital Elixir
15 ml
Belladonna Tincture
25 ml
Aromatic Elixir
60 ml
Purified water
q.s.
100 ml
Sig. One tsp. b.i.d.
If Phenobarbital elixir contains 0.5 % of phenobarbital, how many milligrams of
phenobarbital would be taken daily?
2. How many milligrams of cocaine should be used in compounding the following
prescription?
Cocaine
0.2%
Mineral oil
ad
50 g
Sig. Nasal spray
3. How many grams of potassium iodide are represented in each dose of the following
prescription?
Sol. Potassium Iodide
50%
30 ml
Sig. 1 ml in 10 ml of water a.c.
4. How many grams each of iodine and potassium iodide should be used in
compounding the prescription?
Iodine
1%
Potassium Iodide
2%
Glycerin
ad
500 g
5. Methotrexate sodium injection contains 25 mg of methotrexate sodium per milliliter.
What is the percent concentration of methotrexate in the injection?
6. How many milligrams of salicylic acid and how many milliliters of resorcinol
monoacetate should be used in compounding the prescription?
Salicylic acid
0.1%
Resorcinol Monoacetate
3%
Isopropyl Alcohol
ad
250 ml
Sig. For the scalp.
7. Paregoric contains the equivalent of 0.4% opium. How many milligrams of opium
are represented in a tablespoonful dose of a mixture of equal parts of paregoric and
Kaopectate?
8. Belladonna leaf contains 0.3% of alkaloids. If 10 g of leaf are used to prepare 100
ml of Belladonna tincture, how many milligrams of alkaloids are contained in this
volume of the tincture?
PHCY 6106Teixeira 1 Percentage/Ratio Strength
PRACTICE PROBLEMS
9. One liter of Purified water is mixed with 5 Lb.. (1 Lb.=454 g) of wool fat. Calculate
the percentage (w/w) of purified water in the finished product.
10. What is the percentage strength (w/w) each of Iodochlorhydroxyquin and
Hydrocortisone in the prescription?
Iodochlorhydroxyquin
0.9 g
Hydrocortisone
0.15 g
Cream base
ad
30 g
11. How many grams of salicylic acid and how many milligrams of menthol should be
used in compounding the prescription?
Salicylic acid
2%
Menthol
¼%
Talc
ad
60 g
12. From the following formula calculate the quantity, in grams, of each ingredient,
required to prepare 250 suppositories :
Benzocaine
0.8%
Ephedrine sulfate
0.2%
Zinc oxide
4%
Camphor
2.1%
Cocoa butter
ad
2g
13. Phenobarbital Elixir
60 ml
Aludrox Suspension
180 ml
Sig. Two teaspoonful t.i.d.
If Phenobarbital elixir contains 0.4% of phenobarbital,
a) How many milligrams of phenobarbital would be contained in each dose of the
prescription?
b) How many grams of phenobarbital would be taken if the prescribed dosage regimen
were followed for 1 week?
14. Plasma protein fraction (PPF) is available as a 5% (w/v) solution. If the dose of the
solution for a child is given as 5 ml per Lb., how many grams of PPF would be
administered to a child weighing 20 kg? (1 kg=2.2 Lb.)
15. A vaginal foam contains 0.01% (w/v) of dienestrol. Express this concentration as a
ratio strength.
16. A tetracycline syrup is preserved with 0.08% (w/v) of methylparaben, 0.02%(w/v)
of propylparaben and 0.10% (w/v) of sodium metabisulfite. Express these
concentrations as ratio strengths. PHCY 6106Teixeira 2 Percentage/Ratio Strength
PRACTICE PROBLEMS
17. An injection contains 5 mg/ml (w/v) of lidocaine hydrochloride and 25 μg/ml (w/v)
of epinephrine. Express the concentration of lidocaine hydrochloride as a percentage
and that of epinephrine as ratio strength.
18. A sample of white petrolatum contains 10 mg of Tocopherol per kg as a
preservative. Express the amount of tocopherol as a ratio strength.
19. Dibucaine Hydrochloride solution is used for spinal anesthesia in a concentration of
1:1500 (w/v). How many milligrams of dibucaine hydrochloride are contained in a
20 ml vial of the solution?
20. What is the concentration (percentage and ratio) of Epinephrine in the following
compounded prescription?
Epinephrine solution 1:1000
7.5 ml
Simple syrup
ad
60 ml
21. A hospital pharmacist adds 10 ml of a 20% (w/v) solution of potassium iodide to
500 ml of D%W for parenteral infusion. What is the percentage strength of
potassium iodide in the infusion solution?
22. Insulin injection is preserved with 0.25% (w/v) of metacresol.
a) Express this concentration as a ratio strength.
b) Calculate the quantity, in milligrams, of metacresol in a 20 ml vial of the
injection.
23. If a dry powder mixture of the antibiotic Amoxicillin is diluted with water to 80 ml by
a pharmacist in order to prepare a prescription containing 125 mg Amoxicillin per 5
ml,
a) How many grams of Amoxicillin are there in the dry mixture?
b) What is the percentage strength of Amoxicillin in the filled prescription?
24. How many milliliters of a 70% (w/w) solution having a specific gravity of 1.2 will be
needed to prepare 600 ml of a 10% (w/v) solution?
25. If 10 ml of a Nitroglycerin injection (5 mg of nitroglycerin per ml) is used to make a
liter of an intravenous fluid, what is the percentage strength (w/v) of Nitroglycerin in
the final product?
26. How many milligrams of gentian violet should be used in preparing the following
solution:
Gentian violet solution 1:10,000 (w/v)
500 ml
Sig. Instill as directed. PHCY 6106Teixeira 3 ...
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 Fall '10
 Teixeira
 Kilogram, ml, phenobarbital

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