Neomycin Polymyxin Is Ototoxic
Yes, neomycin polymyxin is definitively ototoxic and can cause irreversible damage to the vestibulocochlear nerve, resulting in permanent hearing loss and vestibular dysfunction. 1
Mechanism and Risk of Ototoxicity
Neomycin, an aminoglycoside antibiotic, is known to cause ototoxicity through:
- Damage to sensory cells and neurons in the inner ear through free radical generation 2
- Irreversible vestibulocochlear nerve damage 1
- Primarily cochleotoxic effects (affecting hearing more than balance) 2
The ototoxicity typically manifests as:
- Hearing loss (often detected first)
- Tinnitus
- Vertigo
- Loss of balance 1
Risk Factors for Ototoxicity
Several factors increase the risk of neomycin-induced ototoxicity:
- Renal impairment - significantly increases risk 3, 4
- Prolonged use - higher risk with extended treatment 1
- Advanced age - elderly patients are more susceptible 1, 3
- Concurrent use of other ototoxic medications such as:
- Loop diuretics (ethacrynic acid, furosemide)
- Other aminoglycosides
- Vancomycin
- Cisplatin 3
Routes of Administration and Risk
Ototoxicity can occur with multiple routes of administration:
- Oral administration - systemic absorption occurs even with oral neomycin 3, 5
- Topical application - can cause severe, permanent hearing deficit, especially with:
- Prolonged application
- Application to large surface areas
- Application to damaged skin or mucous membranes 4
- Ear drops - can cause severe inner ear damage when applied to the middle ear through a perforated tympanic membrane 6
Monitoring Recommendations
For patients receiving neomycin (especially high-risk patients):
- Baseline audiometry before starting treatment 1
- Monthly audiometric testing during treatment 1
- Final audiometry 2 months after the final dose 1
- Monitor for early symptoms of ototoxicity:
- Changes in hearing
- Tinnitus
- Vertigo
- Balance problems 1
Important Clinical Considerations
- Ototoxicity is often delayed in onset - symptoms may not appear until after treatment has ended 3
- Hearing loss is typically irreversible once it occurs 1, 3
- Ototoxicity on audiogram is defined as a 20 dB loss from baseline at any one test frequency or a 10 dB loss at any two adjacent test frequencies 1
- If ototoxicity is detected, neomycin should be discontinued immediately, but the hearing loss that has occurred is likely permanent 1
Prevention Strategies
- Avoid use in patients with known renal impairment 3
- Avoid concurrent use with other ototoxic medications 1, 3
- Use for the shortest duration possible 3
- Consider alternative antibiotics in high-risk patients 3
- Monitor renal function regularly during treatment 1
- Instruct patients to report any auditory or vestibular symptoms immediately 1
Neomycin polymyxin should be used with extreme caution, especially in high-risk populations, and only when the benefits clearly outweigh the significant risk of permanent hearing loss.