Amoxicillin Dosing for Otitis Media in a 6-Year-Old, 20 kg Child
For this 6-year-old child weighing 20 kg with otitis media, prescribe high-dose amoxicillin at 80-90 mg/kg/day divided into two doses, which equals 1600-1800 mg/day total (800-900 mg twice daily), administered for 10 days. 1
Specific Dosing Calculation
- Total daily dose: 80-90 mg/kg/day × 20 kg = 1600-1800 mg/day 1
- Divided dosing: 800-900 mg twice daily (every 12 hours) 1
- Duration: 10 days for children younger than 6 years with any severity, or children 6 years and older with severe symptoms 2
- This dose is well below the maximum safe daily dose of 4000 mg/day (2000 mg twice daily) 1
Rationale for High-Dose Therapy
- High-dose amoxicillin (80-90 mg/kg/day) achieves adequate middle ear fluid concentrations against drug-resistant Streptococcus pneumoniae, with approximately 87% of isolates susceptible to high-dose versus only 83% for standard-dose therapy 1
- High-dose amoxicillin achieves 92% eradication of S. pneumoniae from middle ear fluid, including penicillin-nonsusceptible strains 3
- The American Academy of Pediatrics specifically recommends high-dose amoxicillin as first-line therapy for acute otitis media in the current era of antibiotic resistance 1, 4
Clinical Monitoring and Follow-Up
- Reassess at 48-72 hours if symptoms do not improve or worsen 4
- Address pain management regardless of antibiotic choice 1
- Persistent middle ear effusion without acute symptoms (otitis media with effusion) is common after treatment (60-70% at 2 weeks, 40% at 1 month) and does not require additional antibiotics 2
Treatment Failure Management
If the child fails to improve within 48-72 hours, switch to high-dose amoxicillin-clavulanate (90 mg/kg/day of amoxicillin component with 6.4 mg/kg/day clavulanate), which for this 20 kg child equals 1800 mg amoxicillin/128 mg clavulanate daily, divided into two doses 1, 4
- This provides superior coverage against β-lactamase-producing Haemophilus influenzae and Moraxella catarrhalis, which account for 62-85% of high-dose amoxicillin failures 3, 5
- High-dose amoxicillin-clavulanate achieves 96% eradication of S. pneumoniae and 89.7% eradication of H. influenzae (including β-lactamase producers) 5
For persistent failure after amoxicillin-clavulanate, consider intramuscular ceftriaxone 50 mg/kg/day (1000 mg daily for this child) for 3-5 days 1, 4
Common Pitfalls to Avoid
- Do not use standard-dose amoxicillin (40-45 mg/kg/day) as it provides inadequate coverage for resistant organisms in most communities 1, 4
- Avoid macrolides (azithromycin, clarithromycin) for otitis media, as they have only 20-25% effectiveness against major AOM pathogens and achieve only 80.4% eradication of S. pneumoniae compared to 96% with amoxicillin-clavulanate 4, 5
- Do not prescribe the 7:1 ratio amoxicillin-clavulanate formulations (higher clavulanate content) if treatment escalation is needed, as they significantly increase diarrhea risk without improving efficacy 4