What is the recommended antibiotic treatment for a 5-month-old infant with an ear infection, considering a dosage of 80mg/kg per day?

Acute Otitis Media Treatment in a 5-Month-Old Infant

For a 5-month-old infant with acute otitis media, prescribe high-dose amoxicillin-clavulanate (Augmentin) at 90 mg/kg/day of the amoxicillin component divided into 2 doses for 10 days. 1

Why High-Dose Therapy is Essential for This Age Group

Children under 2 years with acute otitis media require antibiotic therapy and specifically warrant the high-dose formulation. 1 This is not optional—infants in this age group are at highest risk for treatment failure and complications. 1

Key Risk Factors Present in This Patient:

• Age <2 years (this 5-month-old meets the highest-risk criterion) 1
• Infants have incompletely developed immune systems and are more likely to harbor resistant organisms 2, 3

Exact Dosing Calculation

The high-dose regimen is 90 mg/kg/day of amoxicillin with 6.4 mg/kg/day of clavulanate in 2 divided doses (BID). 1 This provides a 14:1 ratio of amoxicillin to clavulanate. 1

For a typical 5-month-old weighing approximately 7-8 kg:

• Total daily dose: 630-720 mg of amoxicillin divided into 2 doses 1
• Per-dose amount: 315-360 mg twice daily 1
• Using the 125 mg/5 mL suspension: approximately 12.5-14.5 mL twice daily 4

For infants under 3 months, the maximum recommended dose is 30 mg/kg/day divided every 12 hours due to immature renal function, but at 5 months, the full 90 mg/kg/day regimen is appropriate. 4

Treatment Duration

The treatment duration must be 8-10 days for children under 2 years of age. 5, 1 Shorter courses (5 days) result in significantly higher clinical failure rates in this age group—34% vs 16% failure with 10-day treatment. 6

Why Not Standard-Dose Amoxicillin Alone?

The most common pathogens in acute otitis media are Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. 2, 3

• Standard-dose amoxicillin (40 mg/kg/day) is inadequate to eradicate resistant S. pneumoniae, particularly in infants. 7
• β-lactamase-producing H. influenzae and M. catarrhalis require the clavulanate component for coverage. 1
• The high-dose formulation (90/6.4 mg/kg/day) achieves middle ear fluid concentrations adequate to overcome penicillin-resistant organisms with MICs of 2-4 mg/L. 1

Clinical Monitoring

Expect clinical improvement within 48-72 hours of starting therapy. 1 If no improvement or worsening occurs:

• Re-examine the child 5
• Consider treatment failure and switch to a second-line agent 2
• Perform tympanocentesis if available to guide therapy 5

Common Pitfalls to Avoid

Underdosing is Treatment Failure:

Using standard doses (40-45 mg/kg/day) when high-dose therapy is indicated leads to inevitable treatment failure with resistant organisms. 1 The 80 mg/kg mentioned in your question is closer but still suboptimal—the evidence-based dose is 90 mg/kg/day. 1, 3

Wrong Formulation:

Verify you are prescribing the 14:1 ratio formulation (90/6.4 mg/kg/day), not older formulations with higher clavulanate content that cause more diarrhea. 1 The high-dose formulation causes less diarrhea (25% vs higher rates with other ratios) while maintaining superior efficacy. 1

Duration Errors:

Do not use 5-day courses in infants—this age group requires the full 8-10 days. 5, 1 The evidence shows 5-day treatment results in 17 percentage points higher failure rates. 6

Adverse Effects

Common adverse effects include diarrhea (25% vs 15% placebo) and diaper dermatitis (51% vs 35% placebo). 1 These are generally mild and do not warrant discontinuation. 1

Alternative if Penicillin Allergy

If true penicillin allergy exists, use cefdinir or azithromycin as first-line alternatives. 3 However, confirm the allergy history—many reported "allergies" are actually intolerances or rashes that do not preclude use. 3