Amoxicillin Dosing for Ear Infection in a 12-Year-Old Weighing 48.8 kg
For this 12-year-old patient with an ear infection, administer amoxicillin 90 mg/kg/day divided into two doses (approximately 2200 mg twice daily, not exceeding the maximum of 4000 mg/day), which translates to high-dose amoxicillin for optimal coverage against resistant pathogens commonly causing acute otitis media. 1, 2
Rationale for High-Dose Regimen
High-dose amoxicillin (90 mg/kg/day) is the preferred first-line therapy for acute otitis media in children and adolescents, particularly in areas with high pneumococcal resistance, as it provides adequate coverage against penicillin-resistant Streptococcus pneumoniae and β-lactamase-negative Haemophilus influenzae. 1, 3
The standard 40-45 mg/kg/day dosing has been shown to be inadequate for eradicating resistant S. pneumoniae, especially during viral coinfection, which is common in ear infections. 4
Research demonstrates that high-dose amoxicillin (80-90 mg/kg/day) achieves bacteriologic eradication in 92% of S. pneumoniae cases and 84% of β-lactamase-negative H. influenzae cases. 3
Specific Dosing Calculation
- For a 48.8 kg patient: 48.8 kg × 90 mg/kg/day = 4,392 mg/day total
- However, the absolute maximum daily dose is 4000 mg/day regardless of weight. 2, 5
- Therefore, administer 2000 mg (2 grams) twice daily (every 12 hours), which equals the maximum allowable dose of 4000 mg/day. 1, 5
Treatment Duration and Monitoring
Complete a full 10-day course of therapy for acute otitis media to ensure adequate bacterial eradication and prevent recurrence. 1, 5
Clinical improvement should be evident within 48-72 hours; if no improvement occurs by this timeframe, reevaluation is necessary and consideration should be given to switching to amoxicillin-clavulanate for β-lactamase-producing organisms. 1, 3
The medication should be taken at the start of meals to minimize gastrointestinal intolerance. 5
Important Clinical Considerations
If the patient has received antibiotics within the past 4-6 weeks, high-dose amoxicillin-clavulanate (90 mg/6.4 mg per kg per day of the amoxicillin component) may be more appropriate to cover β-lactamase-producing organisms. 6, 1
Approximately 34% of H. influenzae isolates in acute otitis media are β-lactamase producers, which would fail amoxicillin monotherapy but respond to amoxicillin-clavulanate. 3
For penicillin-allergic patients with non-anaphylactic reactions, cephalosporins such as cefdinir or cefuroxime are appropriate alternatives; for Type I hypersensitivity reactions, azithromycin or clarithromycin may be used, though they have inferior bacteriologic efficacy. 6, 7
Common Pitfalls to Avoid
Do not use standard-dose amoxicillin (40-45 mg/kg/day) for acute otitis media in the current era of antimicrobial resistance, as it provides inadequate middle ear fluid concentrations against resistant pathogens. 4, 3
Avoid premature discontinuation of therapy even if symptoms improve before 10 days, as this increases risk of recurrence and promotes resistance. 1, 5
Do not exceed 4000 mg/day total amoxicillin dose regardless of weight-based calculations. 2, 5