A drug is packaged as 2 mg per 10 mL. A dose of 0.5 mg is prescribed. How many milliliters should be administered?

A drug is packaged as 2 mg per 10 mL. A dose of 0.5 mg is prescribed. How many milliliters should be administered?

• A. 0.1 mL
• B. 0.25 mL
• C. 1.0 mL
• D. 2.5 mL

Answer: (D)

Converting the drug’s concentration into a volume to administer. The preparation has 2 mg in 10 mL, which is 0.2 mg per 1 mL. To deliver 0.5 mg, you need 0.5 mg ÷ 0.2 mg/mL = 2.5 mL. You can also see this with a quick proportion: 2 mg/10 mL = 0.5 mg/x mL, giving x = 2.5 mL. So the correct volume to administer is 2.5 mL.

Converting the drug’s concentration into a volume to administer. The preparation has 2 mg in 10 mL, which is 0.2 mg per 1 mL. To deliver 0.5 mg, you need 0.5 mg ÷ 0.2 mg/mL = 2.5 mL. You can also see this with a quick proportion: 2 mg/10 mL = 0.5 mg/x mL, giving x = 2.5 mL. So the correct volume to administer is 2.5 mL.