The effects of ototopical steroid, NSAID, and antihistamine on rat auditory function

Abstract

Objectives: Ototopical application of medication for the treatment of a variety of otologic disorders is becoming commonplace. With the increased use of ototopical agents, auditory toxicity must be analyzed. Our objective was to study the effects of transtympanic injection of steroid, NSAID, or antihistamine on Sprague-Dawley rat auditory function. Methods: Twelve Sprague-Dawley rats had their auditory function assessed through ABR. The rats were randomly divided into 6 groups (n = 2 each group): dexamethasone, rimexalone, patanol, astelin, diclofenac, and gentamycin (positive control). Baseline ABR were recorded prior to transtympanic injection and again recorded at 1 and 7 days after treatment. Wave 1 latency and amplitude were measured at 80, 60, 40, and 20 dB using click stimulus. The gentamycin group received an additional 10 days of intramuscular gentamycin after the initial treatment in order to demonstrate significant latency shift. Results: The steroid, antihistamine, and NSAID groups did not demonstrate shifts in wave 1 latency at postinjection day 1 or 7. The gentamycin group revealed a significant latency shift and decrease in amplitude at 40 and 20 db on postinjection day 1. Ten days of intramuscular gentamycin significantly shifted the latency of wave 1 compared to pretreatment. Conclusion: Single dose steroid, NSAID, and antihistamine do not demonstrate a significant ABR latency shift. Transtympanic gentamycin causes a temporary latency shift and amplitude reduction at low intensity stimulus with a return in function at 1 week posttreatment. Performing ABR in the Sprague-Dawley rat is an excellent model to assess auditory toxicity from transtympanic injection.