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Published on: November 26, 2015
[Experimental cochlear damage by neomycin ear drops]
Abstract:
Damage caused by neomycin sulphate solution, identical in concentration to that in ear drops, was tested on the cochleas of 28 guinea pigs. Neomycin sulphate with dexamethasone sodium, and physiologic salt solutions were also tested. Only neomycin solutions damaged the cochlea, and even after only a single exposure. The damage after a single exposure was to the supporting cells and not to the hair cells. However, because of the importance of the supporting cells for normal hearing and because destruction of supporting cells leads to shedding of hair cells, the resulting functional impairment is similar. As a result of further exposure to neomycin the hair cells themselves are damaged, and there is also loss of cell hair. Damage to either the cells or to the hair causes hearing loss. From our work it is clear that in guinea pigs neomycin is absorbed from the middle ear into the inner ear and damages the cochlea. Increased exposure to neomycin increases the damage.
Insights
Neomycin ear drops can damage the cochlea in guinea pigs, affecting hearing. Even a single exposure damages supporting cells, leading to hearing loss.
Area of Science:
- Ototoxicity
- Auditory Neuroscience
- Pharmacology
Background:
- Neomycin sulfate is a common antibiotic used in ear drops.
- Potential ototoxicity of neomycin sulfate necessitates investigation into its effects on the cochlea.
Purpose of the Study:
- To evaluate the cochlear damage caused by neomycin sulfate solution at concentrations found in ear drops.
- To determine the effects of varying exposure levels of neomycin sulfate on cochlear structures.
Main Methods:
- Cochlear damage was assessed in 28 guinea pigs following exposure to neomycin sulfate solutions.
- Control solutions included neomycin sulfate with dexamethasone sodium and physiologic salt solutions.
Main Results:
- Neomycin sulfate solutions, but not controls, caused cochlear damage, even after a single exposure.
- Initial damage targeted supporting cells, progressing to hair cell damage and hair loss with increased exposure.
- Neomycin was absorbed from the middle ear to the inner ear, causing cochlear damage.
Conclusions:
- Neomycin sulfate exhibits ototoxic properties, damaging the cochlea through absorption from the middle ear.
- Damage to supporting cells and/or hair cells by neomycin sulfate leads to hearing loss.
- Increased exposure duration to neomycin sulfate exacerbates cochlear damage and hearing impairment.
