Amoxicillin-Clavulanate Dosing for a 5-Year-Old, 21 kg Child
For a 5-year-old child weighing 21 kg, prescribe 10.5 mL of the 250 mg/5 mL suspension twice daily (every 12 hours) for standard infections, or 10.5 mL twice daily using high-dose formulation if treating otitis media, sinusitis, or lower respiratory tract infections.
Dose Calculation
The FDA-approved dosing for amoxicillin-clavulanate in children ≥3 months depends on infection severity 1:
For Standard (Less Severe) Infections:
- Dose: 25 mg/kg/day divided every 12 hours
- Calculation: 21 kg × 25 mg/kg/day = 525 mg/day total
- Per dose: 525 mg ÷ 2 = 262.5 mg per dose
- Volume: 262.5 mg ÷ 50 mg/mL = 5.25 mL twice daily
However, the 250 mg/5 mL suspension you have is the 125 mg/5 mL formulation equivalent (older ratio formulation). For practical dosing with this suspension:
- Give 10 mL twice daily (provides 500 mg/day amoxicillin component)
For More Severe Infections (Otitis Media, Sinusitis, Lower Respiratory Tract):
- Dose: 45 mg/kg/day divided every 12 hours 1
- Calculation: 21 kg × 45 mg/kg/day = 945 mg/day total
- Per dose: 945 mg ÷ 2 = 472.5 mg per dose
- Volume: 9.5 mL twice daily (rounds to 10 mL for practical administration)
Dosing Regimen
The every 12-hour (twice daily) regimen is strongly preferred as it is associated with significantly less diarrhea compared to three-times-daily dosing 1.
Administration Instructions:
- Give at the start of meals to enhance clavulanate absorption and minimize gastrointestinal side effects 1
- Continue for 5-10 days depending on the infection type (10 days for acute otitis media) 1
- Shake suspension well before each dose
Important Caveats
Formulation Confusion Warning:
The 250 mg/5 mL suspension contains 250 mg amoxicillin + 62.5 mg clavulanate per 5 mL. This is NOT interchangeable with the 250 mg tablet formulation (which contains 125 mg clavulanate) 1. Ensure you're using the correct suspension formulation.
High-Dose Considerations:
For pneumococcal infections with suspected resistance, or for children with:
- Recent antibiotic use (within 30 days)
- Daycare attendance
- Age <2 years
- Moderate-to-severe illness
Consider using 80-90 mg/kg/day formulations (400 mg/5 mL suspension if available), though this exceeds your current 250 mg/5 mL formulation capacity 2, 3.
Weight-Based Dosing Disparity:
Be aware that at 21 kg, this child is at the weight where clinicians often inadvertently underdose. Research shows larger children frequently receive declining mg/kg doses, while smaller children cluster around recommended doses 4. Do not cap at arbitrary "adult maximum" doses for this weight category.
Alternative Every 8-Hour Regimen:
If using the older every-8-hour dosing: 20 mg/kg/day ÷ 3 = approximately 7 mL three times daily for standard infections, or 40 mg/kg/day for severe infections = approximately 11 mL three times daily 1. However, this increases diarrhea risk and is not preferred.