Amoxicillin Dosing for a 20-Pound Patient
For a 20-pound (9 kg) child, the recommended amoxicillin dose is 200-400 mg twice daily (approximately 45-90 mg/kg/day divided into 2 doses), depending on the severity of infection and local resistance patterns. 1
Weight-Based Dosing Calculation
A 20-pound patient weighs approximately 9 kg. The dosing depends on infection severity and risk factors:
Standard-Dose Regimen (Mild Infections, Low Risk)
- 25 mg/kg/day divided every 12 hours = approximately 110 mg twice daily 1
- This translates to roughly 2.2 mL of 125 mg/5 mL suspension twice daily 1
- Appropriate for children ≥2 years without recent antibiotic use and not attending daycare 2
High-Dose Regimen (Moderate-Severe Infections, High Risk)
- 45 mg/kg/day divided every 12 hours = approximately 200 mg twice daily 1
- This translates to roughly 4 mL of 125 mg/5 mL suspension twice daily 1
- For severe infections or high-resistance areas: 80-90 mg/kg/day = approximately 360-400 mg twice daily 2, 3
- This translates to roughly 7-8 mL of 125 mg/5 mL suspension twice daily 1
When to Use High-Dose Amoxicillin
High-dose therapy (80-90 mg/kg/day) is indicated for: 2
- Age <2 years 2
- Daycare attendance 2
- Recent antibiotic use (within 30 days) 2
- Moderate to severe illness 2
- Communities with >10% penicillin-nonsusceptible Streptococcus pneumoniae 2
Age-Specific Considerations
For patients <3 months (12 weeks), the maximum recommended dose is 30 mg/kg/day divided every 12 hours due to immature renal function. 1 However, a 20-pound patient is likely older than 3 months, making standard pediatric dosing appropriate.
Practical Administration
- Give at the start of meals to minimize gastrointestinal side effects 1
- Shake suspension well before each use 1
- Can mix with formula, milk, fruit juice, or water if needed, but administer immediately 1
- Refrigeration is preferable but not required; discard after 14 days 1
Duration of Therapy
- Minimum 10 days for Streptococcus pyogenes infections to prevent acute rheumatic fever 1, 3
- Continue 48-72 hours beyond symptom resolution 1
- For acute otitis media and sinusitis: typically 10-14 days 2
Common Pitfall to Avoid
Do not substitute two 250 mg tablets for one 500 mg tablet when using amoxicillin-clavulanate formulations, as this results in excessive clavulanate dosing and increased gastrointestinal side effects. 3