What is the appropriate treatment for a patient with otitis externa (inflammation of the outer ear) presenting with a greenish discharge, considering the use of polymyxin (antibiotic) neomycin (antibiotic) dexamethasone (corticosteroid)?

Treatment of Otitis Externa with Greenish Discharge

For otitis externa with greenish discharge (suggesting Pseudomonas aeruginosa infection), polymyxin-neomycin-dexamethasone is an appropriate and effective first-line topical treatment when the tympanic membrane is intact, achieving clinical cure rates of 87-95%. 1, 2

Greenish Discharge: Clinical Significance

• Greenish discharge strongly suggests Pseudomonas aeruginosa infection, which causes 20-60% of otitis externa cases and is the most common pathogen alongside Staphylococcus aureus (together responsible for 98% of cases). 1, 3
• The polymyxin-neomycin combination provides excellent coverage against both P. aeruginosa and S. aureus, with demonstrated synergistic activity that reduces minimum inhibitory concentrations by 3-4 times compared to single agents. 4

When Polymyxin-Neomycin-Dexamethasone is Appropriate

Use this combination ONLY when the tympanic membrane is confirmed intact, as neomycin is ototoxic and contraindicated with perforation or tympanostomy tubes. 1, 5

• The dexamethasone component significantly reduces swelling and hastens pain relief compared to antibiotic-only preparations, particularly in moderately severe cases or infections lasting more than 2 days. 1, 6
• Clinical trials demonstrate 87-94% cure rates with this combination, equivalent to fluoroquinolone alternatives. 2, 7

Critical Pre-Treatment Steps

• Perform aural toilet first by removing debris, cerumen, and inflammatory material using gentle suction or dry mopping to ensure medication reaches infected tissues—this is essential for treatment success. 1, 8
• Avoid aggressive irrigation in diabetic or immunocompromised patients, as this can trigger necrotizing otitis externa; use atraumatic suctioning under microscopic guidance instead. 1, 8

Proper Administration Protocol

• Instill 3-4 drops into the affected ear 3-4 times daily for 7-10 days. 5, 9
• Warm the bottle in hands for 1-2 minutes, have the patient lie with affected ear upward, fill the canal completely, and maintain position for 3-5 minutes with gentle tragal pumping to eliminate trapped air. 1
• Complete the full 7-day course even if symptoms resolve earlier to prevent relapse. 1

Pain Management

• Prescribe acetaminophen or NSAIDs for mild-to-moderate pain, as pain typically improves within 48-72 hours of starting topical therapy. 1, 8
• NSAIDs administered during the acute phase significantly reduce pain compared to placebo. 1

When to Switch to Fluoroquinolones Instead

If tympanic membrane integrity is uncertain or compromised, use ONLY non-ototoxic fluoroquinolones (ofloxacin 0.3% or ciprofloxacin 0.2%) instead of polymyxin-neomycin-dexamethasone. 1, 9

• Fluoroquinolones are equally effective (93-96% cure rates) and avoid ototoxicity risk. 1, 7
• Ofloxacin maintains consistent susceptibility patterns, whereas resistance to neomycin and polymyxin B has been increasing, with mean MICs rising above breakpoints in recent studies. 3

Important Caveats and Pitfalls

• Neomycin causes contact dermatitis in 5-15% of patients with chronic otitis externa—avoid in patients with known hypersensitivity or history of contact dermatitis. 1, 5
• If symptoms worsen or fail to improve within 48-72 hours, consider fungal co-infection (especially in diabetics), allergic contact dermatitis from neomycin, inadequate drug delivery, or incorrect diagnosis. 1, 10
• This preparation is contraindicated in fungal and viral infections of the external canal—greenish discharge with white fuzzy debris suggests mixed bacterial-fungal infection requiring antifungal therapy. 10, 2

When Systemic Antibiotics Are Needed

Reserve oral antibiotics (fluoroquinolones like ciprofloxacin) for specific circumstances only: 1

• Extension of infection beyond the ear canal (periauricular swelling)
• Diabetes mellitus or immunocompromised status
• When topical therapy cannot reach the infected area
• Treatment failure after 48-72 hours

Special Populations Requiring Modified Management

• Diabetic or immunocompromised patients: Monitor carefully for necrotizing otitis externa, consider adding systemic antibiotics even for seemingly uncomplicated cases, and use atraumatic suctioning instead of irrigation. 1, 8
• Patients over 58 years: Assess for diabetes or immunocompromised status as risk factors for progression to necrotizing otitis externa. 8

Reassessment Criteria

• If no improvement within 48-72 hours, reassess for inadequate drug delivery due to canal obstruction, poor adherence, fungal co-infection, neomycin contact dermatitis, or misdiagnosis. 1, 8
• Suspect fungal otitis externa if patient initially improved but then worsened, especially with recent antibiotic use or diabetes. 10