Amoxicillin Dosing for Acute Otitis Media in a 14-Year-Old
For a healthy 14-year-old with acute otitis media, prescribe high-dose amoxicillin 80–90 mg/kg/day divided into two doses (given every 12 hours) for 10 days. 1, 2
Dosing Calculation and Administration
- Calculate the total daily dose by multiplying the adolescent's weight in kilograms by 80–90 mg/kg, then divide this total into two equal doses administered 12 hours apart. 1
- For example, a 50 kg adolescent would receive 4,000–4,500 mg total daily, split into 2,000–2,250 mg twice daily.
- The twice-daily regimen is preferred because it is associated with significantly less diarrhea compared to three-times-daily dosing while maintaining equivalent clinical efficacy. 3, 4
Rationale for High-Dose Therapy
- High-dose amoxicillin achieves middle ear fluid concentrations that exceed the minimum inhibitory concentration for approximately 87% of Streptococcus pneumoniae isolates (including intermediately resistant strains), compared to only 83% coverage with standard dosing. 1, 2
- This regimen provides adequate antimicrobial coverage against the three principal pathogens of acute otitis media: Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. 1
When to Switch to Amoxicillin-Clavulanate
Consider high-dose amoxicillin-clavulanate (90 mg/kg/day amoxicillin + 6.4 mg/kg/day clavulanate in a 14:1 ratio, divided twice daily) as first-line therapy if:
- The patient received amoxicillin within the preceding 30 days 1, 2
- Concurrent purulent conjunctivitis is present 1
- Coverage for β-lactamase-producing Haemophilus influenzae or Moraxella catarrhalis is specifically needed 2
The 14:1 formulation causes significantly less diarrhea than older 7:1 formulations while preserving efficacy against β-lactamase-producing organisms. 1
Management of Treatment Failure
- Reassess the diagnosis if no clinical improvement occurs within 48–72 hours. 1, 2
- If the initial regimen was amoxicillin alone, switch to high-dose amoxicillin-clavulanate (90 mg/kg/day amoxicillin + 6.4 mg/kg/day clavulanate, divided twice daily). 1, 2
- If the patient fails amoxicillin-clavulanate, consider ceftriaxone 50 mg/kg administered intramuscularly or intravenously for three days. 1, 2
Treatment Duration
- Prescribe a 10-day course for acute otitis media in adolescents, consistent with American Academy of Pediatrics recommendations. 1, 2, 3
Common Pitfalls to Avoid
- Do not substitute two 250 mg/125 mg tablets for one 500 mg/125 mg tablet of amoxicillin-clavulanate, as both contain the same amount of clavulanic acid (125 mg) and are not equivalent. 3
- Avoid using standard-dose amoxicillin (40–45 mg/kg/day) in the current era of increasing antibiotic resistance, as high-dose therapy provides superior coverage against drug-resistant S. pneumoniae. 1, 2
- Ensure adequate pain management regardless of antibiotic choice, as symptom relief is an important component of acute otitis media treatment. 1