Recommended Amoxicillin Dosage for Otitis Media
For a 5-year-old child weighing 35 pounds (15.9 kg) with acute otitis media, prescribe amoxicillin 80-90 mg/kg/day divided into 2 doses, which equals approximately 640-720 mg twice daily (total daily dose 1,272-1,430 mg). 1
Dose Calculation
- Weight conversion: 35 pounds = 15.9 kg
- High-dose amoxicillin calculation: 80-90 mg/kg/day × 15.9 kg = 1,272-1,430 mg/day 1, 2
- Practical dosing: Administer 650-700 mg twice daily (approximately 82-88 mg/kg/day) 1, 2
- Divided dosing: Give in 2 divided doses, 12 hours apart 1, 3
Rationale for High-Dose Therapy
High-dose amoxicillin (80-90 mg/kg/day) is the first-line treatment for acute otitis media because it provides effective coverage against drug-resistant Streptococcus pneumoniae while maintaining excellent safety, low cost, acceptable taste, and narrow microbiologic spectrum. 1, 2
- This dosing achieves middle ear fluid concentrations adequate to overcome penicillin-resistant S. pneumoniae, which accounts for 10-15% of upper respiratory isolates nationally 1
- High-dose therapy eradicates S. pneumoniae in 92-96% of cases, including nonsusceptible strains 1, 4
- Standard-dose amoxicillin (40-45 mg/kg/day) is insufficient in areas with >10% prevalence of nonsusceptible S. pneumoniae 1
Treatment Duration
- For children ≥2 years with uncomplicated AOM: 5-7 days of therapy is sufficient 2
- For children <2 years or with severe symptoms: 10 days of therapy is recommended 1
- Reassess at 48-72 hours if symptoms fail to improve 1, 2
When to Use Amoxicillin-Clavulanate Instead
Switch to high-dose amoxicillin-clavulanate (90 mg/kg/day of amoxicillin component with 6.4 mg/kg/day clavulanate) if: 1, 2
- The child received amoxicillin in the previous 30 days
- Concurrent purulent conjunctivitis is present (otitis-conjunctivitis syndrome)
- Coverage for β-lactamase-producing Haemophilus influenzae or Moraxella catarrhalis is desired
- The child attends daycare (higher risk for resistant organisms) 1
- The child is <2 years old with moderate-to-severe illness 1
Treatment Failure Management
If no improvement occurs by 48-72 hours, consider treatment failure and switch therapy: 1, 2
- First-line failure: Switch to amoxicillin-clavulanate (90 mg/kg/day of amoxicillin with 6.4 mg/kg/day clavulanate) 1
- Second-line failure: Administer ceftriaxone 50 mg/kg IM/IV daily for 3 days 1
- β-lactamase-producing H. influenzae is the most common cause of amoxicillin treatment failure, accounting for 62-64% of bacteriologic failures 4
Important Clinical Considerations
- Pain management should be addressed concurrently during the first 24 hours of antibiotic therapy 2
- Penicillin allergy: Recent data show cross-reactivity between penicillins and second/third-generation cephalosporins is minimal (<1%), making cefdinir, cefuroxime, or cefpodoxime safe alternatives 1
- Once versus twice daily dosing: Both regimens show comparable efficacy, but twice-daily dosing is standard for high-dose therapy 3
- Compliance: Twice-daily dosing improves adherence compared to three-times-daily regimens 3