A bottle states '250 mg/5 mL.' How many mL are needed for a 1 g dose?

• A. 20 mL
• B. 10 mL
• C. 5 mL
• D. 15 mL

Answer: (A)

When a preparation lists a drug amount per a volume, the dose is proportional to the volume. Here, 250 mg are in every 5 mL, so the concentration is 250 mg/5 mL = 50 mg per mL. To give 1 g (1000 mg), determine the volume needed: 1000 mg ÷ 50 mg/mL = 20 mL. Another way: 1 g is four times 250 mg, so you need four times the 5 mL portion, which is 4 × 5 mL = 20 mL. Therefore, 20 mL are needed.