Pharmacy PEBC Practice Exam

A physician wants to switch a terminally-ill patient from slow release morphine sulphate tablets, 15 mg po twice daily, to a liquid morphine sulphate dosage form because the patient has difficulty in swallowing tablets. If a morphine sulphate 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. 20 mL

2. 60 mL

3. 100 mL

4. 120 mL

The correct answer is: 120 mL

The physician wants to switch the patient from 15 mg slow release tablets twice daily to 5 mg solution every 4 hours. This means the patient will be receiving the same amount of morphine every day, but in smaller, more frequent doses. In a 20 day supply, the patient will need to take the medication approximately 120 times (every 4 hours, 6 times per day, for 20 days). Therefore, the volume dispensed should be 120 mL to provide the same pain relief as the tablet regimen. The other options are incorrect because they do not take into account the smaller, more frequent doses needed in the liquid form to match the same daily amount of medication.