Page 39 - A guide to dosage form 1_full v3

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) (Practical Guide…)

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)

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