Chapter 9. General dosage calculations (1 of 32) Sample Questions

1. A physician wants to switch a terminally-ill patient from slow-release Morphine sulphate tablets, 15 mg twice daily, to a liquid Morphine sulfate dosage form because the patient has difficulty in swallowing tablets. If a morphine sulfate solution containing 5 mg per mL is prescribed q4h, what volume should be dispensed for a 20-day supply to provide the same pain relief as the tablet regimen?
  1. A. 20 mL
  2. B. 60 mL
  3. C. 80 mL
  4. D. 100 mL
  5. E. 120 mL
Ans: E
Working:
(5 mg)/(1 mL) x 6 times daily = 6 mL
6 mL x 20 days = 120 mL
Or
i.15 mg BID = 30 mg daily
ii.For 20 days: 30 mg x 20 = 600 mg are dispensed
Solution contains 5 mg/mL. 600 mg are contained in 600/5 = 120 mL