What is the dose of neomycin (antibiotic)/polymyxin B (antibiotic) sulfate for otitis externa?

Dosing of Neomycin/Polymyxin B for Otitis Externa

For otitis externa, neomycin/polymyxin B sulfate with hydrocortisone should be administered as 3-4 drops into the affected ear canal three to four times daily for 7-10 days. 1, 2

Administration Guidelines

• Topical therapy is the mainstay of treatment for uncomplicated acute otitis externa, delivering antimicrobial concentrations 100-1000 times higher than systemic therapy 3
• For neomycin/polymyxin B/hydrocortisone otic suspension, the standard dosing is:
  • Adults: 3-4 drops into the affected ear canal four times daily 1, 4
  • Children: 3 drops into the affected ear canal four times daily 1, 4
• Treatment duration is typically 7-10 days, with clinical improvement expected within 48-72 hours of initiating appropriate therapy 5, 2

Proper Administration Technique

• Have the patient lie with the affected ear upward 3
• Administer drops along the side of the ear canal until it is filled 3
• Patient should remain in this position for 3-5 minutes 3
• Gentle to-and-fro movement of the pinna may be necessary to eliminate trapped air 3
• Alternative method includes tragal pumping to aid in getting drops into the ear canal 3

Efficacy and Considerations

• Neomycin/polymyxin B/hydrocortisone is effective against common pathogens in otitis externa, including Pseudomonas aeruginosa and Staphylococcus aureus 5, 1
• Clinical cure rates with neomycin/polymyxin B/hydrocortisone range from 83.9% to 97% in clinical trials 1, 2, 4
• Eradication rates for Pseudomonas aeruginosa, the most common pathogen, are approximately 100% 1

Important Precautions

• Neomycin has been associated with contact sensitivity in 13-30% of patients with chronic otitis externa 3
• Avoid use in patients with non-intact tympanic membranes (perforation or tympanostomy tubes) due to potential ototoxicity 3
• Ensure the ear canal is clear of debris before administration; aural toilet may be necessary to improve penetration of drops 3
• Consider alternative treatments like quinolone preparations if there are concerns about neomycin sensitivity or ototoxicity 1, 2

Alternative Formulations

• Once-daily ofloxacin otic solution (0.3%) has shown equivalent efficacy to neomycin/polymyxin B/hydrocortisone administered four times daily, with the advantage of less frequent dosing and no risk of ototoxicity 1
• Ciprofloxacin 0.3%/dexamethasone 0.1% otic suspension administered twice daily has demonstrated superior clinical and microbiological outcomes compared to neomycin/polymyxin B/hydrocortisone administered three times daily 2

Treatment Failure Considerations

• If no improvement occurs within 48-72 hours, consider:
  • Treatment failure due to inadequate drug delivery 3
  • Allergic contact dermatitis to neomycin or other components 3
  • Fungal co-infection requiring antifungal therapy 3
  • Misdiagnosis or alternative etiology 3

Remember that topical therapy alone is sufficient for uncomplicated otitis externa, and systemic antibiotics should not be prescribed as initial therapy unless there is extension outside the ear canal or specific host factors indicating a need for systemic therapy 3, 5.