A medication is supplied as 250 mg per 5 mL. If you need to administer 150 mg, how many milliliters should be drawn?

A medication is supplied as 250 mg per 5 mL. If you need to administer 150 mg, how many milliliters should be drawn?

• A. 2 mL
• B. 4 mL
• C. 3 mL
• D. 5 mL

Answer: (C)

You determine how much volume to draw by using the concentration of the medication. The solution is 250 mg in 5 mL, which equals 50 mg per mL. To deliver 150 mg, divide the dose by the concentration: 150 mg ÷ 50 mg/mL = 3 mL. Cross-check with cross-multiplication: 250 mg/5 mL = 150 mg/x mL gives x = (150 × 5) / 250 = 3 mL. Back-calculate to confirm: 3 mL × 50 mg/mL = 150 mg. Draw 3 mL.

You determine how much volume to draw by using the concentration of the medication. The solution is 250 mg in 5 mL, which equals 50 mg per mL. To deliver 150 mg, divide the dose by the concentration: 150 mg ÷ 50 mg/mL = 3 mL. Cross-check with cross-multiplication: 250 mg/5 mL = 150 mg/x mL gives x = (150 × 5) / 250 = 3 mL. Back-calculate to confirm: 3 mL × 50 mg/mL = 150 mg. Draw 3 mL.