Amoxicillin Dosing for Acute Otitis Media in a 5-Year-Old, 23 kg Child
For this 5-year-old child weighing 23 kg with an ear infection, prescribe high-dose amoxicillin at 80-90 mg/kg/day divided into two doses, which equals 1,840-2,070 mg total daily (920-1,035 mg twice daily), given for 10 days. 1, 2
Dosing Calculation and Rationale
Calculate the exact dose by multiplying 23 kg × 80-90 mg/kg = 1,840-2,070 mg per day, split into two equal doses of 920-1,035 mg given every 12 hours. 2
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 (penicillin MIC 0.12-1.0 μg/mL), compared to only 83% coverage with standard dosing. 1
This dosing provides adequate coverage against the three major pathogens causing acute otitis media: Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. 1, 3
Treatment Duration
Treat for 10 days in children younger than 6 years of age. 2, 4
Clinical improvement should be evident within 48-72 hours; if no improvement occurs or symptoms worsen, reassess the diagnosis and consider treatment failure. 2, 4
When to Use Amoxicillin-Clavulanate Instead
Switch to high-dose amoxicillin-clavulanate (90 mg/kg/day amoxicillin + 6.4 mg/kg/day clavulanate in the 14:1 ratio formulation, divided twice daily) if any of the following apply:
- The child received amoxicillin within the previous 30 days 1, 2, 4
- Concurrent purulent conjunctivitis is present 2, 4
- The child attends daycare (increased risk of β-lactamase-producing organisms) 2
- No clinical improvement after 48-72 hours on amoxicillin alone 2, 4
For this 23 kg child, amoxicillin-clavulanate dosing would be 2,070 mg amoxicillin with 147 mg clavulanate per day, divided into two doses. 5
Management of Treatment Failure
If symptoms persist or worsen after 48-72 hours on high-dose amoxicillin, first reassess the diagnosis to confirm acute otitis media. 2
If diagnosis is confirmed and initial therapy was amoxicillin alone, switch to high-dose amoxicillin-clavulanate. 2, 4
If the child fails amoxicillin-clavulanate, administer ceftriaxone 50 mg/kg intramuscularly or intravenously for 3 days. 2, 4
Important Clinical Caveats
The 14:1 ratio formulation of amoxicillin-clavulanate (90/6.4 mg/kg/day) is critical because it causes significantly less diarrhea than older formulations with higher clavulanate content (7:1 ratio), while maintaining efficacy against β-lactamase-producing organisms. 1, 5, 4
High-dose amoxicillin-clavulanate demonstrates 96% eradication of S. pneumoniae from middle ear fluid at days 4-6, significantly superior to azithromycin. 1, 5
β-lactamase-producing H. influenzae is the predominant pathogen in treatment failures with amoxicillin monotherapy, occurring in 62-64% of bacteriologic failures. 6
Address pain management with appropriate analgesia regardless of antibiotic choice. 2, 3