Toxicity of ototopical drugs: animal modeling.

It is important to be aware of the potential ototoxicity of any drug, vehicle, or antiseptic that is used in the middle ear. Frequently used ear drops (Cortisporin otic suspension, Coly-Mycin S Otic, and VoSoL otic solution) were studied for their ototoxicity. Compound action potentials were measured before and at 1, 2, and 24 hours following drug application on the round window membranes of chinchillas. Each drug was applied for 10 minutes and then was removed by rinsing. The sound pressure in decibels sound pressure level that produced a compound action potential amplitude of 10 microV was defined as the threshold. The change in threshold was interpreted as hearing loss. On the basis of the short-term results at 24 hours following drug application, the ototoxicity of Coly-Mycin was calculated to be twice that of Cortisporin, and the ototoxicity of VoSoL four times that of Cortisporin.