It is not thought to be as ototoxic as neomycin. Gentamicin is presently the biggest problem antibiotic with respect to ototoxicity as most of the other ototoxic antibiotics have been replaced. Gentamicin was released for clinical use in the earlier 1960's. Vestibulotoxicity is the major problem rather than hearing toxicity. Certain persons with mitochondrial deletions in the 12S subunit are much more susceptable to Gentamicin than the general population.
Occasional persons do appear to have substantial vestibular toxicity from Vancomycin.
The reason why occasional persons are more sensitive is not clear but might resemble the situation with Gentamicin where there is a susceptability mutation. Ear drops may contain antibiotics, some of which can be ototoxic when administered to persons with perforated ear drums. Cortisporin otic solution appears to be the most ototoxic to the cochlea of guinea pigs, with much less toxicity for gentamicin drops. The vestibulotoxicity of ear drops has so far not been studied, although case reports suggest that gentamicin containing drops are toxic. There are several known interactions.