A vial contains 50 mg in 2 mL. How many milliliters are required to administer a 150 mg dose?

• A. 3 mL
• B. 4 mL
• C. 2 mL
• D. 6 mL

Answer: (D)

Focus on concentration and proportional dosing. The vial has 50 mg in 2 mL, which equals 25 mg per mL. To deliver 150 mg, you need 150 mg ÷ 25 mg/mL = 6 mL. Another way: 150 mg is three times the 50 mg, so use three times the volume: 2 mL × 3 = 6 mL. Check: 6 mL × 25 mg/mL = 150 mg. For context, 3 mL would give 75 mg, 4 mL would give 100 mg, and 2 mL would give 50 mg, confirming why 6 mL is correct.