Vestibular and Cochlear Ototoxicity of Topical Agents

Topical preparations applied locally to the ear are widely used for the treatment and prophylaxis of external and middle ear infections. Examples of such preparations include antibacterial agents such as aminoglycosides, anti fungal agents and antiseptics used before surgery. These agents have the potential to cross the round window membrane into the middle ear in patients with tympanic membrane perforations or ventilation tubes. Some of these agents may adversely affect the cochlear and the vestibular parts of the inner ear. Most of the data on topical ototoxicity is based on animal studies. Our group has developed an animal model using auditory and vestibular evoked potentials in order to assess possible inner ear damage. During the past years our animal model was used to examine the effects of antiseptics, antimycotics, aminoglycosides and hydrogen peroxide showing clear results with respect to the cochlear and vestibular otoxicity in some of the preparations. In addition, there is clear clinical evidence of topical ototoxicity in humans. Of special interest is vestibular ototoxicity which is under reported because of central compensation leading to short lasting clinical symptoms. Both clinical data and animal research resulted in recommendations for the use of topical ear drops by the American and British Academies of Otolaryngology. These recommendations will be reviewed with special focus on medico legal issues.