First-Line Antibiotic for Ear Infections
Amoxicillin at 80-90 mg/kg/day (divided twice or three times daily) is the first-line antibiotic for acute otitis media in children when antibiotics are indicated, and amoxicillin-clavulanate 500-875 mg twice daily is first-line for adults. 1, 2
Treatment Algorithm by Patient Age and Type of Infection
Children with Acute Otitis Media
Initial antibiotic selection depends on recent antibiotic exposure and clinical presentation:
Standard first-line: Prescribe amoxicillin 80-90 mg/kg/day when the child has NOT received amoxicillin in the past 30 days, does NOT have concurrent purulent conjunctivitis, and is NOT allergic to penicillin 1
Enhanced coverage needed: Prescribe amoxicillin-clavulanate (or another antibiotic with β-lactamase coverage) when the child HAS received amoxicillin in the past 30 days, HAS concurrent purulent conjunctivitis, or has recurrent AOM unresponsive to amoxicillin 1
Observation option: For children 6 months to 2 years with non-severe illness and uncertain diagnosis, OR children ≥2 years without severe symptoms, consider observation for 48-72 hours with symptomatic treatment only 1
The high-dose amoxicillin recommendation (80-90 mg/kg/day) is critical because it achieves adequate middle ear fluid concentrations against penicillin-intermediate Streptococcus pneumoniae, which is a major pathogen in AOM. 1 Recent data confirms that despite microbiologic changes in AOM etiology, amoxicillin maintains lower treatment failure rates (1.7%) compared to amoxicillin-clavulanate (11.3%), cefdinir (10.0%), or azithromycin (9.8%). 3
Adults with Acute Otitis Media
Amoxicillin-clavulanate is the antibiotic of choice for acute otitis media in adults, with standard dosing of 500-875 mg twice daily, providing coverage against penicillin-intermediate S. pneumoniae, β-lactamase-producing H. influenzae, and M. catarrhalis. 2 For patients with recent antibiotic exposure or moderate disease, use high-dose formulation of 4 g amoxicillin/250 mg clavulanate per day. 4
Penicillin Allergy Management
For non-Type I hypersensitivity reactions (no anaphylaxis, no Stevens-Johnson syndrome):
- Children: Prescribe cefdinir, cefpodoxime, or cefuroxime 1, 5
- Adults: Prescribe cefdinir, cefuroxime, or cefpodoxime with standard adult dosing 5
The historical 10% cross-reactivity rate between penicillins and cephalosporins is a significant overestimate based on outdated data; modern evidence shows second- and third-generation cephalosporins have distinct chemical structures making cross-reactivity approximately 0.1%. 5 This means you can confidently prescribe these agents for patients with non-severe penicillin reactions (rash, mild GI symptoms). 5
For true Type I hypersensitivity (anaphylaxis):
- Adults: Prescribe respiratory fluoroquinolones (levofloxacin 500 mg daily or moxifloxacin 400 mg daily) with 90-92% predicted efficacy 2, 4
- Children: Consider azithromycin, though it has lower efficacy with 20-25% bacteriologic failure rates possible 2, 5
Reassessment and Treatment Failure
Reassess at 48-72 hours if symptoms worsen or fail to improve:
- Confirm the diagnosis is truly AOM and exclude other causes 1
- If initially managed with observation, begin antibiotics 1
- If initially treated with amoxicillin, switch to amoxicillin-clavulanate or another agent with β-lactamase coverage 1
- Do NOT continue the same antibiotic beyond 72 hours without improvement 4
Critical Pitfalls to Avoid
Do not prescribe oral antibiotics for uncomplicated otitis externa (swimmer's ear)—this is the most common error. 2, 4 Otitis externa requires topical antibiotic drops (ofloxacin or ciprofloxacin-dexamethasone), which deliver 100-1000 times higher antibiotic concentration than oral therapy. 2, 4
Do not avoid all cephalosporins based solely on reported penicillin allergy without clarifying the reaction type. 5 This leads to unnecessary use of broader-spectrum agents like fluoroquinolones and contributes to antimicrobial resistance. 5
Do not use first-generation cephalosporins (cephalexin, cefazolin) in penicillin-allergic patients, as these have higher cross-reactivity due to similar side-chain structures. 5
In diabetic or immunocompromised patients with ear pain, do not miss necrotizing otitis externa, which requires urgent systemic antibiotics and imaging. 2, 4
For children, do not prescribe doses below 80 mg/kg/day of amoxicillin, as this is inadequate for resistant pneumococci. 1 However, be aware that in obese children, the calculated dose may exceed the standard adult dose of 1500 mg/day—prescribing patterns vary among experts on whether to cap at adult dosing. 6