A 5-year-old boy is prescribed amoxicillin 250 mg/5 mL suspension at a dose of 500 mg three times a day for 7 days, for a chest infection. Each bottle is 100 mL. What is an appropriate number of bottles to dispense to ensure he can complete the course?

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

Answer: (C)

The key idea is to translate the prescribed amount into a total volume we must dispense, using the suspension’s concentration, and then see how many bottles are needed.

Total amoxicillin required: 500 mg per dose × 3 times daily × 7 days = 10,500 mg. The suspension contains 250 mg in 5 mL, which is 50 mg/mL. So the volume needed is 10,500 mg ÷ 50 mg/mL = 210 mL. Each bottle is 100 mL, so two bottles provide 200 mL (not enough). Three bottles provide 300 mL, which covers the 210 mL required.

Alternative check: per-dose volume is 500 mg ÷ (50 mg/mL) = 10 mL; daily volume is 30 mL; over 7 days = 210 mL. Either way, three bottles are needed.