An amoxicillin 400 mg/5 mL suspension; a 4-year-old child requires amoxicillin 90 mg/kg/day in divided doses every 12 hours for 5 days. What bottle size should be dispensed?

• A. 75 mL
• B. Do not fill
• C. 50 mL
• D. 100 mL

Answer: (D)

The essential idea is to translate a weight-based dose into a total volume of suspension using the drug’s concentration, then choose a bottle size that can supply that total volume for the full course.

First find the total amount of amoxicillin the child should receive: 90 mg per kg per day, for 5 days. That’s 450 mg per kg over the course. The suspension is 400 mg per 5 mL, which is 80 mg/mL. So the total volume needed over 5 days is 450 mg/kg ÷ 80 mg/mL = 5.625 mL/kg.

For a typical 4-year-old (about 18 kg), the required volume is 5.625 mL/kg × 18 kg ≈ 101 mL. Among common bottle sizes, a 100 mL bottle is the closest that would typically cover the course for many children of this age, whereas smaller bottles (50 or 75 mL) would likely be insufficient. The option to “do not fill” is not appropriate for a prescribed course.