What antibiotics (ATB) are used to treat otitis externa?

Treatment of Otitis Externa

Topical antimicrobial therapy is the definitive first-line treatment for uncomplicated acute otitis externa, NOT oral antibiotics. 1

First-Line Topical Antibiotics

The most effective topical preparations target Pseudomonas aeruginosa and Staphylococcus aureus, which cause 98% of cases 1, 2:

Fluoroquinolone Preparations (Preferred)

• Ciprofloxacin 0.2% otic solution: Instill 0.25 mL twice daily for 7 days 3

  • 100% effective against P. aeruginosa in clinical studies 4
  • Safe for use with tympanic membrane perforation or tympanostomy tubes (non-ototoxic) 1, 3
  • FDA-approved for acute otitis externa 3

• Ofloxacin 0.3%: Alternative fluoroquinolone with similar efficacy 1

  • Also non-ototoxic and safe with uncertain tympanic membrane integrity 1

Aminoglycoside Combinations (Alternative)

• Neomycin/Polymyxin B (with or without hydrocortrocortisone): Effective alternative 1
  • Demonstrates synergistic activity with 3-4 fold reduction in MIC compared to single agents 5
  • CAUTION: 5-15% of patients develop contact dermatitis to neomycin 1
  • CONTRAINDICATED with tympanic membrane perforation due to ototoxicity risk 1
  • 100% of P. aeruginosa isolates are resistant to neomycin alone, but the combination with polymyxin B overcomes this 4, 5

Critical Pre-Treatment Step

Perform aural toilet (debridement) before administering drops to ensure medication reaches infected tissues 1, 6. This includes:

• Gentle suction
• Dry mopping
• Irrigation to remove obstructing debris 1

When to Use Systemic (Oral) Antibiotics

Reserve oral antibiotics ONLY for these specific indications 1:

• Extension of infection beyond the ear canal
• Diabetes mellitus or immunocompromised status
• Topical therapy cannot reach infected area
• Treatment failure with topical therapy after 48-72 hours

When systemic antibiotics are indicated, use fluoroquinolones (e.g., ciprofloxacin orally) for Pseudomonas and S. aureus coverage 1. Most commonly prescribed oral antibiotics (amoxicillin, trimethoprim) are 100% inactive against P. aeruginosa and should be avoided 4, 7.

Special Populations Requiring Modified Treatment

Tympanic Membrane Perforation or Tubes

Use ONLY non-ototoxic fluoroquinolones (ciprofloxacin or ofloxacin) 1, 3. Avoid all aminoglycoside-containing preparations 1.

Diabetes or Immunocompromised Patients

• Consider adding systemic fluoroquinolones to topical therapy 1
• Monitor closely for necrotizing otitis externa 1
• Higher risk for fungal co-infection (otomycosis) 1, 6

Fungal Otitis Externa (Otomycosis)

Treat with topical antifungals (not antibiotics) plus thorough debridement 6:

• Voriconazole for Aspergillus infections 6
• Boric acid as alternative 6
• Avoid antibacterial drops that promote fungal overgrowth 1, 6

Treatment Efficacy and Expected Course

• Topical therapy achieves 65-90% clinical resolution within 7-10 days 1
• Topical antibiotics deliver 100-1000 times higher drug concentrations than oral antibiotics 1, 2
• Pain typically improves within 48-72 hours 1
• Clinical cure rates: topical antibiotics 77-96% vs. oral antibiotics 30-67% 1

Common Pitfalls to Avoid

• Overuse of oral antibiotics: 20-40% of patients inappropriately receive oral antibiotics that are often inactive against causative pathogens 1, 7
• Using ototoxic preparations (aminoglycosides) with perforated tympanic membrane 1
• Failure to perform debridement before administering drops 1, 6
• Missing fungal infections in patients with diabetes or treatment failure 1, 6
• Inadequate pain management: Prescribe appropriate analgesics (acetaminophen, NSAIDs, or stronger agents based on severity) 1

Treatment Failure Management

If no improvement at 48-72 hours, consider 1:

• Inadequate drug delivery due to canal obstruction (repeat debridement)
• Poor adherence to therapy
• Allergic contact dermatitis (especially with neomycin preparations)
• Fungal co-infection
• Incorrect diagnosis