Amoxicillin Dosing for Acute Otitis Media in a 2-Year-Old
For a 2-year-old child weighing 14.8 kg with acute otitis media, prescribe high-dose amoxicillin at 80-90 mg/kg/day divided into two doses, which equals 592-666 mg twice daily (approximately 600-665 mg every 12 hours) for 10 days. 1
Rationale for High-Dose Therapy
This child has multiple indications for high-dose amoxicillin therapy:
- Age under 2 years is an automatic indication for high-dose therapy (80-90 mg/kg/day rather than standard 40-45 mg/kg/day), as recommended by the American Academy of Pediatrics 1
- High-dose amoxicillin achieves middle ear fluid concentrations adequate to overcome penicillin-resistant Streptococcus pneumoniae with altered penicillin-binding proteins 1
- The high-dose regimen provides predicted clinical efficacy of 90-92% against penicillin-resistant S. pneumoniae 2
Specific Dosing Calculation
For this 14.8 kg child:
- Lower end (80 mg/kg/day): 14.8 kg × 80 mg = 1,184 mg/day ÷ 2 doses = 592 mg twice daily 1
- Upper end (90 mg/kg/day): 14.8 kg × 90 mg = 1,332 mg/day ÷ 2 doses = 666 mg twice daily 1
Practical Prescribing
- Divide the total daily dose into 2 equal doses given every 12 hours 1
- Duration: 10 days of therapy for children under 2 years with AOM 3, 1
- Amoxicillin can be given without regard to meals, though administration with meals may improve gastrointestinal tolerability 1
- The maximum single dose is 2 g, which is not a concern for this patient 1
Using Oral Suspension
If using amoxicillin 250 mg/5 mL suspension:
- For 600 mg dose: approximately 12 mL twice daily
- For 665 mg dose: approximately 13.3 mL twice daily
If using amoxicillin 125 mg/5 mL suspension:
- For 600 mg dose: approximately 24 mL twice daily
- For 665 mg dose: approximately 26.6 mL twice daily
Evidence Supporting High-Dose Therapy
Research demonstrates that standard-dose amoxicillin (40 mg/kg/day) is inadequate to effectively eradicate resistant Streptococcus pneumoniae, particularly during viral coinfection, with a dosing regimen of 75-90 mg/kg/day recommended for AOM 4. A prospective study showed that high-dose amoxicillin (80 mg/kg/day) achieved eradication in 92% of S. pneumoniae isolates, including 75% that were nonsusceptible to penicillin 5.
Reassessment and Treatment Failure
- Reassess the patient if symptoms worsen or fail to improve within 48-72 hours 1
- If treatment fails, switch to high-dose amoxicillin-clavulanate (90 mg/kg/day of amoxicillin component with 6.4 mg/kg/day clavulanate in 2 divided doses) 1
- The predominant pathogens isolated from children failing high-dose amoxicillin therapy are beta-lactamase-producing organisms, particularly Haemophilus influenzae 5
Pain Management
Address pain management regardless of antibiotic use, especially during the first 24 hours, as recommended by the American Academy of Family Physicians 1
Common Pitfalls to Avoid
- Do not use standard-dose amoxicillin (40-45 mg/kg/day) in children under 2 years old 1
- Do not use amoxicillin-clavulanate as first-line therapy unless the child received amoxicillin in the previous 30 days or has otitis-conjunctivitis syndrome 1
- Ensure proper reconstitution of oral suspension and shake well before each use 6
- Verify the suspension concentration (125 mg/5 mL vs 250 mg/5 mL) before calculating volume to avoid dosing errors 2