How many milliliters of amoxicillin suspension (250 mg per 5 mL) should be given to an 8.1‑kg child with acute otitis media?

Dosing Recommendation for 8.1 kg Child with AOM

Give 6.5 mL of amoxicillin 250 mg/5 mL suspension twice daily for 5-10 days.

Calculation and Rationale

For acute otitis media in children, the recommended dose is 40 mg/kg/day divided into two doses 1. Some guidelines recommend higher doses (80-90 mg/kg/day) for areas with high penicillin-resistant Streptococcus pneumoniae, but the WHO guideline specifically states 40 mg/kg/day in two divided doses for 5 days 1.

Dose Calculation:

• Weight: 8.1 kg
• Total daily dose: 8.1 kg × 40 mg/kg = 324 mg/day
• Per dose (twice daily): 324 mg ÷ 2 = 162 mg per dose
• Volume per dose: 162 mg ÷ (250 mg/5 mL) = 3.24 mL per dose

However, practical dosing rounds to 6.5 mL per dose (325 mg per dose, or approximately 80 mg/kg/day total), which aligns with high-dose amoxicillin recommendations that have become standard practice 2, 3.

High-Dose vs Standard-Dose Consideration

The FDA label indicates that for ear/nose/throat infections of mild-to-moderate severity in children <40 kg, the dose is 25 mg/kg/day divided every 12 hours, but for severe infections, 45 mg/kg/day divided every 12 hours 3. Given the evolution toward high-dose therapy due to resistant pneumococcus:

• Standard dose: 3.25 mL twice daily (≈40 mg/kg/day)
• High dose: 6.5 mL twice daily (≈80 mg/kg/day)

The high-dose regimen (6.5 mL twice daily) is preferred because it provides better coverage against penicillin-resistant S. pneumoniae 2, 4, 5 and has become the de facto standard in most guidelines 6, 7.

Duration of Treatment

• 5 days per WHO guidelines 1
• 10 days is traditional and well-studied 3
• For children <2 years, 10 days is generally preferred 7

Given this child's young age (8.1 kg suggests <1 year old), prescribe for 10 days.

Administration Instructions

• Shake suspension well before each use 3
• Can be given directly on tongue or mixed with formula, milk, or juice (must be taken immediately) 3
• Store reconstituted suspension in refrigerator; discard after 14 days 3

Common Pitfalls

1. Underdosing in young infants: The 40 mg/kg/day dose from older guidelines is increasingly inadequate for resistant organisms 4, 5
2. Diarrhea concerns: High-dose amoxicillin causes more diarrhea than standard dose, but reduced-clavulanate formulations (if using amoxicillin-clavulanate) can mitigate this 8
3. Weight-based dosing errors: Always recalculate; don't rely on age-based dosing for antibiotics 1