What is the recommended dosage of amoxicillin (amoxicillin) for a 90-pound (weight) female child with an ear infection, considering her weight and potential medical history?

Amoxicillin Dosing for Ear Infection in a 90-Pound Girl

For a 90-pound (41 kg) girl with an ear infection, the recommended dose is 90 mg/kg/day of amoxicillin divided into two doses, which equals approximately 1,845 mg twice daily (not to exceed 2,000 mg per dose). 1

Weight-Based Calculation

• A 90-pound child weighs approximately 41 kg 1
• Using the high-dose regimen: 90 mg/kg/day × 41 kg = 3,690 mg total daily dose 1
• This translates to 1,845 mg twice daily (every 12 hours) 1
• The maximum single dose should not exceed 2,000 mg, so this patient would receive the full calculated dose 1

Rationale for High-Dose Therapy

High-dose amoxicillin (80-90 mg/kg/day) is strongly recommended as first-line therapy for acute otitis media in children. 1, 2 This dosing regimen is specifically indicated for:

• Children with recent antibiotic use (within the past 30 days) 1
• Daycare attendance 1
• Age under 2 years 1
• Geographic areas with >10% penicillin-resistant Streptococcus pneumoniae 2
• Moderate to severe illness 1

The high-dose regimen achieves middle ear fluid concentrations adequate to overcome penicillin-resistant S. pneumoniae and provides coverage against β-lactamase-producing Haemophilus influenzae and Moraxella catarrhalis. 1, 3

When to Use Amoxicillin-Clavulanate Instead

Switch to amoxicillin-clavulanate (90 mg/kg/day of amoxicillin component with 6.4 mg/kg clavulanate) if: 1

• The patient received antibiotics within the past 4-6 weeks 4
• Treatment failure occurs after 48-72 hours on amoxicillin alone 2
• Severe illness at presentation 2
• Recurrent or persistent otitis media 3

For this patient, amoxicillin-clavulanate would provide 1,845 mg of amoxicillin component twice daily with 131 mg of clavulanate twice daily. 1

Treatment Duration and Monitoring

• Continue treatment for 10 days for acute otitis media 1, 2
• Clinical improvement should be evident within 48-72 hours 1, 5
• If no improvement or worsening occurs after 48-72 hours, reevaluate and consider switching to amoxicillin-clavulanate or investigating for complications 1
• Complete the full course even if symptoms improve before completion 2

Practical Administration

For a dose of approximately 1,845 mg twice daily:

• Using 400 mg/5 mL suspension: approximately 23 mL twice daily 6
• Using 875 mg tablets: two tablets twice daily (1,750 mg per dose, slightly under target but acceptable) 6
• Administer at the start of meals to minimize gastrointestinal intolerance 6

Common Pitfalls to Avoid

• Do not use standard-dose amoxicillin (40-45 mg/kg/day) for acute otitis media, as this dosing is inadequate to eradicate resistant S. pneumoniae, particularly during viral coinfection 7
• Research demonstrates that standard dosing of 40 mg/kg/day results in insufficient middle ear fluid concentrations, with mean concentrations of only 2.7-5.7 mcg/mL depending on viral coinfection status 7
• The current evidence strongly supports 75-90 mg/kg/day for effective treatment 7
• Verify suspension concentration before calculating volume to avoid dosing errors 1
• Do not substitute two 250 mg tablets for one 500 mg tablet when using amoxicillin-clavulanate formulations, as this results in excessive clavulanate dosing 2

Alternative for Penicillin Allergy

For non-anaphylactic penicillin reactions, cephalosporins such as cefdinir or cefuroxime are appropriate alternatives. 2 For Type I hypersensitivity reactions, azithromycin or clarithromycin may be used, though they have inferior bacteriologic efficacy against resistant pathogens. 2