Page 41 - Course Guide 2019

10 PHARMACEUTICAL CALCULATION EXERCISES

1. How many millilitres of each isopropyl alcohol (IPA) solution that you will need, if you
would want to make 120 mL of a solution with 60% IPA from 70% and 30% IPA
solution? (Answer: 90 mL of 70% IPA and 30mL of 30% IPA solution)
2. You have an injection solution of Drug A 400 mg/mL. You put 10 mL of this solution in
an empty bottle and dilute it with 5 mL of Drug B 2% injection. What is the final
concentration of Drug A and Drug B? (Answer: 266 mg/mL Drug A, 0.007 mg/mL
(0.7%w/v))
3. How many millilitres of water will be needed to dissolve 3 g of a powder drug which is
soluble in 2.5 parts of water? (Answer: 7.5 mL)
4. How many millilitres of water will be needed to dissolve 7 g of a powder drug which is
soluble in 1.5 parts of water? (Answer: 10.5 mL)
5. Powder C is soluble 1:11 in water. How much water will be needed to dissolve 0.37 g
of the powder? (Answer: 4.07 L)
6. 500 micrograms in 5 mL is equal to 1 in x. What is the value of x? (Answer: 10 000)
7. How much of methylene blue powder is necessary to prepare 5 L solution with a
concentration of 1 in 10 000? (Answer: 500 mg)
8. How much potassium chloride will be required to prepare 150 mL of 1: 10 solutions?
(Answer: 15 g)
9. An antibiotic drop was dispensed to a patient (11 months old) with a dose of 0.3 mL. A
dropper was available with the product, which supplies 20 drops per mL. How many
drops should the patient receive each time?
10. What is the concentration of betamethasone in 100 g of 1:20 dilution of betamethasone
in aqueous cream? (Answer: 5 g)
11. Prepare 25 g of a 1 in 5 dilutions of mometasone 1% ointment in yellow soft paraffin.
How much of mometasone 1% will be required to prepare this product? (Answer: 5 g)
12. How much (mg) salicylic acid will be needed to prepare 50 g of an ointment containing
0.75% of salicylic acid in white soft paraffin? (Answer: 375 mg)
13. How much theobroma oil base will be in one suppository, if you are asked to prepare
6 suppositories (1 g each) with 200 mg of zinc oxide BP (displacement value 4.7)?
(Answer: 957.5 mg)
14. Prepare 10 x 1 g suppositories with 60 mg Drug D (displacement value 1.1) with Hard
Fat BP as the base. How much Hard Fat BP will be needed? (Answer: 9.45 g)
15. How many capsules will you dispense to a patient with a prescription of 1 cap t.d.s
2/52?
16. How many capsules will you dispense to a patient with a prescription of 2 cap h.s 1/12?
(Answer: 56 capsules)
17. What is the suitable size of a capsule to dispense 450 mg of powder?
18. You are required to prepare 75 mL 0.2% w/v benzalkonium chloride solution from a
stock solution of 1% w/v. How much of the stock solution will be needed? (Answer: 15
mL)
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19. How much of CuSO .5H2O (MW:249.72) that is required to get 2 g of CuSO
(MW:159.61)? (Answer: 3.13 g)
20. Prepare 120 mL of potassium permanganate solution so that when 100 mL of this
solution is diluted with 100 mL water, produces a solution of 1:4000. (Answer: 3 g of
potassium permanganate).