Amoxicillin Dosing for 12-Month-Old with Acute Otitis Media
For a 12-month-old child (~10 kg) with fever, red tympanic membrane, and ear discharge (indicating acute otitis media with perforation), prescribe high-dose amoxicillin at 80–90 mg/kg/day divided into two doses for 10 days, which equals 800–900 mg total daily (400–450 mg every 12 hours). 1, 2, 3
Specific Dosing Calculation
- Total daily dose: 80–90 mg/kg/day × 10 kg = 800–900 mg/day 1, 2
- Divided dosing: 400–450 mg every 12 hours 1, 2
- Practical administration: Using 125 mg/5 mL suspension, give 16–18 mL every 12 hours 4
- Treatment duration: 10 days for children under 2 years 1, 2, 3
Rationale for High-Dose Therapy
High-dose amoxicillin (80–90 mg/kg/day) achieves middle ear fluid concentrations that reliably overcome penicillin-resistant Streptococcus pneumoniae, the predominant bacterial pathogen in this age group. 2, 3 The high-dose regimen provides coverage for approximately 87% of S. pneumoniae isolates, compared with only 83% for standard dosing. 3 This child has multiple risk factors warranting high-dose therapy: age <2 years and presence of otorrhea (ear discharge), which indicates tympanic membrane perforation and more severe infection. 1, 2
When to Switch to Amoxicillin-Clavulanate
Consider switching to high-dose amoxicillin-clavulanate (90 mg/kg/day amoxicillin + 6.4 mg/kg/day clavulanate in a 14:1 ratio, divided twice daily) if any of the following apply: 1, 2, 3
- The child received amoxicillin within the previous 30 days 1, 2, 3
- No clinical improvement or worsening after 48–72 hours of amoxicillin monotherapy 1, 2, 3
- Concurrent purulent conjunctivitis (otitis-conjunctivitis syndrome) 2, 3
- Daycare attendance or incomplete Haemophilus influenzae type b vaccination 1
The rationale for switching is that β-lactamase-producing H. influenzae (found in 58–82% of isolates) and M. catarrhalis are resistant to amoxicillin alone but susceptible to amoxicillin-clavulanate. 1
Expected Clinical Response and Monitoring
Clinical signs (fever, ear pain, irritability) should begin to improve within 48–72 hours after initiating high-dose amoxicillin. 2, 3 If no improvement or clinical worsening is observed after 48–72 hours, first reassess the diagnosis of acute otitis media, then switch to high-dose amoxicillin-clavulanate. 2, 3 If the child fails to improve on amoxicillin-clavulanate, consider ceftriaxone 50 mg/kg administered intramuscularly or intravenously for three days. 2, 3
Important Clinical Considerations
- Twice-daily dosing is preferred because it is associated with significantly less diarrhea than three-times-daily regimens while maintaining equivalent efficacy. 4, 5, 6
- Administer at the start of meals to enhance absorption of the medication and minimize gastrointestinal intolerance. 4
- The presence of ear discharge (otorrhea) indicates tympanic membrane perforation, which is a marker of more severe infection but does not change the antibiotic choice—high-dose amoxicillin remains first-line. 1, 2
- Pain management should be addressed regardless of antibiotic choice, using age-appropriate analgesics. 3
Common Pitfalls to Avoid
- Do not use standard-dose amoxicillin (40–45 mg/kg/day) in children under 2 years with acute otitis media, as this fails to achieve adequate middle ear fluid concentrations against resistant organisms and promotes treatment failure. 1, 3, 7
- Verify the suspension concentration (125 mg/5 mL vs. 250 mg/5 mL) before calculating volume to avoid dosing errors. 1, 4
- Do not substitute two 250 mg/125 mg tablets for one 500 mg/125 mg tablet in older children, as they contain different ratios of clavulanate and are not equivalent. 4
- Ensure the child is ≥3 months of age before prescribing oral amoxicillin-clavulanate; for infants <3 months with suspected serious bacterial infection, intravenous regimens are preferred. 1