What antibiotic to prescribe for an adult or pediatric patient with an ear infection and a known allergy to penicillin (pcn)?

Antibiotic Selection for Ear Infections in Penicillin-Allergic Patients

For patients with penicillin allergy and ear infections, prescribe cefdinir as first-line therapy if the allergy was non-severe (simple rash, GI upset) or occurred more than 5 years ago, as it has only 0.1% cross-reactivity with penicillin due to dissimilar side chains. 1, 2

Risk Stratification Based on Allergy Type

Non-Severe or Remote Penicillin Allergy

• Cefdinir is the preferred first-line antibiotic for patients whose penicillin allergy involved simple rash, gastrointestinal upset, or occurred more than 5 years ago 2
• Cefdinir has dissimilar side chains to most penicillins, placing it in the low-risk category with approximately 0.1% cross-reactivity 1, 2
• Other safe cephalosporin options include cefuroxime, cefpodoxime, and ceftriaxone, all with negligible cross-reactivity 2, 3, 4

Severe or Recent Immediate-Type Allergy

• If the patient had anaphylaxis, angioedema, or severe urticaria within the past 5 years, cephalosporins with dissimilar side chains (cefdinir, cefuroxime, cefpodoxime) can still be used but require heightened monitoring 1, 2
• The Dutch Working Party (SWAB) guideline provides strong evidence that cephalosporins with dissimilar side chains can be used in immediate-type penicillin allergy regardless of severity 1

When to Avoid All Beta-Lactams

• Never use any cephalosporin if the patient had Stevens-Johnson syndrome, toxic epidermal necrolysis, or other severe delayed reactions to penicillin 1
• Avoid cephalosporins with similar side chains (cephalexin, cefaclor, cefamandole) in patients allergic to amoxicillin, as these share R1 side chains with cross-reactivity rates up to 27% 1, 3

Non-Beta-Lactam Alternatives

Azithromycin as Second-Line Option

• Azithromycin is completely safe in penicillin-allergic patients with zero cross-reactivity 5
• For acute otitis media in adults: 500 mg on day 1, then 250 mg daily for days 2-5 6
• For pediatric acute otitis media: 30 mg/kg as single dose, OR 10 mg/kg daily for 3 days, OR 10 mg/kg day 1 then 5 mg/kg days 2-5 6
• Important caveat: Azithromycin has 20-25% bacteriologic failure rates and substantial pneumococcal resistance in many areas 2

Fluoroquinolones for Adults Only

• Levofloxacin or moxifloxacin have 90-92% predicted efficacy for acute otitis media in adults 2
• Never use fluoroquinolones in pediatric patients due to cartilage toxicity concerns 2

Treatment Algorithm

1. Assess allergy severity and timing: Determine if reaction was immediate vs. delayed, severe vs. non-severe, and when it occurred 1, 7

2. For non-severe or remote allergy (>5 years): Prescribe cefdinir 300 mg twice daily for adults, or weight-based dosing for children 2

3. For severe immediate-type allergy within 5 years: Use cefdinir with heightened monitoring in controlled setting, OR choose azithromycin as safer alternative 1, 2

4. For severe delayed-type reactions: Avoid all beta-lactams; use azithromycin or fluoroquinolones (adults only) 1, 2

5. Assess response at 48-72 hours: If no improvement, escalate to ceftriaxone 50 mg/kg IM/IV for 3 days (safe even with penicillin allergy due to dissimilar side chains) 2, 8

Critical Pitfalls to Avoid

• Do not confuse family history with patient history - only the patient's own allergy matters for treatment decisions 2, 8
• Do not assume all penicillin allergies are true IgE-mediated reactions - approximately 90% of reported penicillin allergies are not confirmed immunologic reactions 7, 9
• Avoid first-generation cephalosporins (cephalexin, cefazolin, cefadroxil) in patients with amoxicillin allergy due to shared side chains with cross-reactivity up to 12.9% 1, 3
• Do not use trimethoprim-sulfamethoxazole or macrolides as first-line due to substantial pneumococcal resistance rates 2

When Cefdinir Fails

• Ceftriaxone 50 mg/kg IM/IV for 3 days is the recommended second-line treatment after cefdinir failure 8
• Ceftriaxone has only 0.1% cross-reactivity with penicillin and provides superior coverage against beta-lactamase-producing organisms 8
• If ceftriaxone fails, consider tympanocentesis for culture-directed therapy or infectious disease consultation 8