Amoxicillin Dosing for a 28.42 kg Child
For a child weighing 28.42 kg, the appropriate amoxicillin dose depends on the indication: for mild-to-moderate infections (otitis media, pharyngitis, skin infections), prescribe 25 mg/kg/day divided every 12 hours (approximately 355 mg per dose, or 7 mL of 250 mg/5 mL suspension twice daily); for severe infections or lower respiratory tract infections requiring high-dose therapy, prescribe 45 mg/kg/day divided every 12 hours (approximately 640 mg per dose, or 12.8 mL of 250 mg/5 mL suspension twice daily). 1
Dosing Algorithm by Clinical Indication
Mild-to-Moderate Infections
- Ear/nose/throat infections, skin/skin structure infections, genitourinary tract infections: 25 mg/kg/day divided every 12 hours OR 20 mg/kg/day divided every 8 hours 1
- For this 28.42 kg child: 710 mg/day total = 355 mg twice daily = 7 mL of 250 mg/5 mL suspension twice daily
- Alternative three-times-daily dosing: 568 mg/day = 189 mg three times daily = 3.8 mL three times daily
Severe Infections or Lower Respiratory Tract Infections
- High-dose amoxicillin indicated for: community-acquired pneumonia, severe otitis media with resistant organisms, or any infection requiring enhanced pneumococcal coverage 2, 1
- Dose: 45 mg/kg/day divided every 12 hours OR 40 mg/kg/day divided every 8 hours 1
- For this 28.42 kg child: 1,279 mg/day total = 640 mg twice daily = 12.8 mL of 250 mg/5 mL suspension twice daily
- Alternative three-times-daily dosing: 1,137 mg/day = 379 mg three times daily = 7.6 mL three times daily
Pneumococcal Infections with Resistance Concerns
- For S. pneumoniae with penicillin MICs >2.0 µg/mL: 90 mg/kg/day divided in 2 doses OR 45 mg/kg/day divided in 3 doses 2, 3
- For this 28.42 kg child: 2,558 mg/day = 1,279 mg twice daily = 25.6 mL of 250 mg/5 mL suspension twice daily
- This exceeds typical adult maximum doses but is guideline-recommended for resistant pneumococcal infections 2
Critical Dosing Considerations
Twice-Daily vs. Three-Times-Daily Dosing
- Twice-daily dosing (every 12 hours) is preferred for improved adherence and comparable efficacy 4, 5, 6
- Recent evidence demonstrates non-inferiority of twice-daily regimens for community-acquired pneumonia 5, 6
- Pharmacokinetic modeling confirms 25 mg/kg/dose q12h provides similar drug exposure to 16.67 mg/kg/dose q8h for most pathogens 4
Duration of Therapy
- Standard duration: 5-7 days for most infections 1
- Shorter 3-day courses may be non-inferior to 7-day courses for uncomplicated community-acquired pneumonia, though cough resolution may be slightly delayed 5, 6
- Streptococcus pyogenes pharyngitis: minimum 10 days to prevent acute rheumatic fever 1
Common Pitfalls to Avoid
- Underdosing larger children: Studies show children >15 kg frequently receive subtherapeutic doses when clinicians cap at "adult maximum doses" 7
- For this 28.42 kg child, do not artificially limit to adult doses (typically 500 mg twice daily) when treating resistant organisms—guideline-based weight-based dosing should be followed 2, 7
- Viral coinfection: Amoxicillin middle ear fluid penetration is reduced during concurrent viral infections, potentially requiring higher doses 8
Administration Instructions
- Take at the start of meals to minimize gastrointestinal intolerance 1
- Shake suspension well before each use 1
- Suspension can be mixed with formula, milk, fruit juice, water, or cold drinks if needed, but must be consumed immediately 1
- Refrigeration is preferable but not required; discard unused suspension after 14 days 1
When to Consider Alternative Antibiotics
- Treatment failure after 48-72 hours: Switch to high-dose amoxicillin-clavulanate (80-90 mg/kg/day of amoxicillin component) to cover β-lactamase-producing organisms 9
- Suspected atypical pathogens (Mycoplasma, Chlamydophila) in children >3 years: Add macrolide therapy 2
- Suspected Staphylococcus aureus: Add clindamycin or switch to cephalexin 2, 3