Ototoxicity of topical gentamicin preparations

Objective: To document that commercially available topical gentamicin-conta ining eardrops carry a risk of ototoxicity if they reach the middle ear thr ough a tympanic membrane defect, Study Design: Clinical study, retrospectiv e case-note review. Setting: Department of Otolaryngology, The Toronto Hosp ital, University of Toronto. Patients: Sixteen patients were identified wit h well-documented histories, physical findings and laboratory investigation s consistent with topical gentamicin-induced ototoxicity. One patient with incapacitating unilateral Meniere's disease underwent successful intentiona l vestibular ablation using topical gentamicin/steroid drops. Results: In a ll eases of inadvertent ototoxicity, patients had used the drops for longer than 7 days (average 20.7 d) prior to symptoms developing. All patients de veloped vestibulotoxicity that was confirmed on ENG testing. Only 1 patient had a noticeable worsening of cochlear reserve. Deliberate and successful therapeutic ablation of vestibular function in a patient with unilateral Me niere's disease confirms the vestibulotoxic nature of commercially availabl e topical gentamicin preparations, Conclusions: Physicians should consider the potential for ototoxicity if gentamicin-containing eardrops (and by ext rapolation all topical aminoglycoside drops) are used for longer than 7 day s in patients with a tympanic membrane defect. These preparations should no t be used in the presence of healthy middle ear mucosa and should be discon tinued shortly after the discharge has stopped. It is important to recogniz e that toxicity is primarily vestibular rather than cochlear.