A 400 mg dose is needed. The preparation is 160 mg per 5 mL. How many milliliters are required?

A 400 mg dose is needed. The preparation is 160 mg per 5 mL. How many milliliters are required?

• A. 12.5 mL
• B. 10 mL
• C. 15 mL
• D. 5 mL

Answer: (A)

You convert dose to volume using the concentration given. The preparation has 160 mg in 5 mL, which is 32 mg per 1 mL. To deliver 400 mg, divide the desired dose by the per-milliliter amount: 400 mg ÷ 32 mg/mL = 12.5 mL. Another way is to multiply by the volume-per-dose: 400 mg × (5 mL / 160 mg) = 12.5 mL. So you need 12.5 mL of the preparation. For context, 10 mL would give 320 mg, 15 mL would give 480 mg, and 5 mL would give 160 mg, illustrating why 12.5 mL is the correct amount for 400 mg.

You convert dose to volume using the concentration given. The preparation has 160 mg in 5 mL, which is 32 mg per 1 mL. To deliver 400 mg, divide the desired dose by the per-milliliter amount: 400 mg ÷ 32 mg/mL = 12.5 mL. Another way is to multiply by the volume-per-dose: 400 mg × (5 mL / 160 mg) = 12.5 mL. So you need 12.5 mL of the preparation. For context, 10 mL would give 320 mg, 15 mL would give 480 mg, and 5 mL would give 160 mg, illustrating why 12.5 mL is the correct amount for 400 mg.