Amoxicillin Dosing for Ear Infection in a 90-Pound Child
For a 90-pound (approximately 41 kg) female child with an ear infection, the recommended liquid amoxicillin dose is 1,640-1,845 mg per day, divided into two doses of 820-922.5 mg every 12 hours, using the high-dose regimen of 80-90 mg/kg/day. 1
Weight-Based Calculation
- The child weighs 90 pounds, which equals approximately 40.9 kg (90 ÷ 2.2 = 40.9 kg)
- Using the recommended high-dose regimen of 80-90 mg/kg/day for acute otitis media: 1
- Lower end: 40.9 kg × 80 mg/kg = 3,272 mg/day (1,636 mg twice daily)
- Upper end: 40.9 kg × 90 mg/kg = 3,681 mg/day (1,840.5 mg twice daily)
- However, since this child weighs more than 40 kg, adult dosing applies: 875 mg every 12 hours for ear/nose/throat infections 2
Practical Liquid Formulation Dosing
For a child weighing >40 kg with an ear infection, the FDA-approved dosing is 875 mg every 12 hours, which translates to 17.5 mL of 250 mg/5 mL suspension twice daily. 2
- If using 250 mg/5 mL suspension: 17.5 mL twice daily (every 12 hours)
- If using 400 mg/5 mL suspension: approximately 11 mL twice daily (every 12 hours)
Rationale for High-Dose Therapy
The high-dose amoxicillin regimen (80-90 mg/kg/day) is specifically recommended for acute otitis media to provide adequate coverage against penicillin-resistant Streptococcus pneumoniae. 1, 3
- The standard 40 mg/kg/day dosing is inadequate to effectively eradicate resistant S. pneumoniae, particularly during viral coinfection 4
- High-dose amoxicillin achieves middle ear fluid concentrations sufficient to overcome organisms with intermediate resistance 5
- The 80-90 mg/kg/day regimen provides clinical efficacy rates of 82% for bacterial eradication in acute otitis media 5
Treatment Duration and Monitoring
Continue treatment for 10 days for children with acute otitis media. 1, 3
- Reassess the patient at 48-72 hours if symptoms persist or worsen 1, 6
- Clinical improvement should be evident within the first 24-48 hours of therapy 1
- If no improvement occurs by 48-72 hours, consider switching to amoxicillin-clavulanate (90 mg/kg/day of amoxicillin component with 6.4 mg/kg/day clavulanate) 1, 6
When to Switch to Amoxicillin-Clavulanate
Consider amoxicillin-clavulanate as first-line therapy if the child has received antibiotics within the past 4-6 weeks, as this increases the likelihood of β-lactamase-producing organisms. 3, 6
- β-lactamase-producing H. influenzae accounts for the majority of treatment failures with amoxicillin alone 5
- High-dose amoxicillin-clavulanate (90 mg/kg/day of amoxicillin with 6.4 mg/kg/day clavulanate in 2 divided doses) provides coverage against resistant organisms 6
Common Pitfalls to Avoid
- Do not use the 875 mg tablet dose if the child weighs less than 40 kg - use weight-based liquid dosing instead 2
- Verify the suspension concentration (125 mg/5 mL, 250 mg/5 mL, or 400 mg/5 mL) before calculating volume to avoid dosing errors 3
- Shake the oral suspension well before each use and ensure proper reconstitution 2
- Administer at the start of a meal to minimize gastrointestinal intolerance 2
- Discard any unused reconstituted suspension after 14 days; refrigeration is preferable but not required 2