What oral antibiotic would you use for otitis externa?

Oral Antibiotics for Otitis Externa

For otitis externa, topical antibiotic therapy is strongly recommended over oral antibiotics, as oral antibiotics have limited utility and should not be prescribed as initial therapy for uncomplicated cases. 1

Understanding Otitis Externa

Acute otitis externa (AOE) is a cellulitis of the ear canal skin and subdermis with acute inflammation and variable edema. Nearly all (98%) cases in North America are bacterial, with the most common pathogens being:

• Pseudomonas aeruginosa (20-60% of cases)
• Staphylococcus aureus (10-70% of cases)
• Often occurring as polymicrobial infections 1

First-Line Treatment Approach

Topical Therapy is Superior to Oral Antibiotics

Topical antimicrobials deliver significantly higher concentrations to the infected tissue (100-1000 times higher than systemic therapy) and are the treatment of choice for otitis externa. 1

Despite this, about 20-40% of patients with AOE receive oral antibiotics, which:

• Are usually inactive against the common pathogens
• May have undesirable side effects
• Contribute to bacterial resistance 1

When Oral Antibiotics Are Appropriate

Oral antibiotics should only be prescribed when:

1. There is extension of infection outside the ear canal
2. Specific host factors necessitate systemic therapy
3. Cellulitis of the pinna or adjacent skin is present
4. Concurrent bacterial infection elsewhere (e.g., sinusitis, pneumonia) exists
5. Signs of severe infection are present (high fever, severe otalgia, toxic appearance)
6. Acute otitis externa persists or worsens despite topical therapy 1

Oral Antibiotic Selection (When Indicated)

If systemic therapy is truly necessary, the oral antibiotic should cover the most common pathogens:

• Ciprofloxacin is the preferred oral agent when Pseudomonas aeruginosa is suspected or confirmed 1, 2, 3
  • Dosage: 750 mg twice daily for adults
  • Provides good tissue penetration and antipseudomonal activity

Caution with Ciprofloxacin

Be aware that resistance to ciprofloxacin is emerging among Pseudomonas strains. In cases of malignant otitis externa (a severe form affecting the skull base), treatment failure with oral ciprofloxacin has been reported, necessitating intravenous therapy 4.

Key Points in Management

1. Aural toilet (cleaning the ear canal) is essential before administering any treatment
2. Topical therapy should be the first-line treatment for uncomplicated otitis externa
3. Pain management is important as otalgia can be severe
4. Monitor response to treatment within 48-72 hours

Common Pitfalls to Avoid

• Prescribing oral antibiotics when topical therapy alone would be sufficient
• Selecting oral antibiotics that don't cover Pseudomonas aeruginosa when needed
• Failing to clean the ear canal before treatment
• Not recognizing when extension beyond the ear canal requires systemic therapy
• Using aminoglycoside-containing eardrops in patients with tympanostomy tubes or perforated eardrums (potential ototoxicity) 1

Prevention Strategies

Preventive measures include:

• Removing obstructing cerumen
• Using acidifying ear drops before/after swimming
• Drying the ear canal with a hair dryer
• Using ear plugs while swimming
• Avoiding trauma to the external auditory canal 1

Remember that bacterial resistance is of less concern with topical therapy than with systemic antibiotics, making topical treatment the safer and more effective option for uncomplicated otitis externa.