CPhT Dosage Calculations 3

Question 1

A nurse requests 250 mL of a 0.9% NaCl solution. How many grams of NaCl are needed to prepare this solution?

Accepted Answer

2.25 g

Answer

0.9% = 0.9 g/100 mL; 0.9 × 2.5 = 2.25 g in 250 mL.

Question 2

An order reads: Morphine 2 mg IV q4h PRN pain. The vial contains 10 mg/mL. How many mL per dose?

Accepted Answer

0.2 mL

Answer

2 mg ÷ 10 mg/mL = 0.2 mL per dose.

Question 3

A pharmacy receives an order for KCl 20 mEq in 100 mL NS. Stock vials contain 2 mEq/mL. How many mL of KCl should be added?

Accepted Answer

10 mL

Answer

20 mEq ÷ 2 mEq/mL = 10 mL of KCl stock.

Question 4

A patient weighing 88 lbs needs a drug dosed at 10 mg/kg. What is the correct dose in mg?

Accepted Answer

400 mg

Answer

88 lbs ÷ 2.2 = 40 kg; 40 kg × 10 mg/kg = 400 mg.

Question 5

How many 250 mg capsules are needed to fill a prescription for amoxicillin 500 mg TID for 10 days?

Accepted Answer

60 capsules

Answer

500 mg ÷ 250 mg = 2 capsules/dose × 3 doses/day × 10 days = 60 capsules.

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