Assesment of castellani solution?s ototoxic effects on guinea pigs using otoacoustic emission and auditory evoked brainstem potentials

Objective: Research seeking an agent that has an intense impact on otomycosis treatment with less ototoxicity has been continuing. Use of topical otomycosis drugs on patients with tympanic membrane perforation has been problematic in ENT practice because of potential ototoxicity. One of the nonspecific topical drug is Castellani?s solution. It is used for fungal external otitis treatment and commonly preferred in Turkey for years. It is likely that guinea pigs are more susceptible to topical ototoxic drugs than are humans. Thus, this research is planned to evaluate ototoxic effects of Castellani?s solution on guinea pigs when used intratimpanically.Material and Methods: Fourteen female adult albino guinea pigs were used in this experiment. Distortion product otoacoustic emissions and auditory evoked brainstem potentials were recorded in order to evaluate the effect of intratympanic injections. All treatments were performed seven consecutive days using intratympanic injection. The first group comprised of the left ears of seven guinea pigs and received 0.2 ml of gentamicin (40 mg/ml (Group 1). The second group comprised of the left ears of the other seven guinea pigs and received 0.1 ml of Castellani?s solution (Group 2). Contralateral ears of all these fourteen guinea pigs were used as negative control group and received 0.2 ml of saline solution intratimpanically for seven consecutive days (Group 3). All these treatments were performed simultaneously. Otomicroscopic evaluation was performed in order to check the external ear canal and tympanic membrane of pigs prior to all recordings. For auditory evoked brainstem potential recordings, standart alternating clicks as well as 6 and 8 kHz tone bursts were delivered through an insert earphone. Distortion product otoacoustic emissions and auditory evoked brainstem potentials were recorded, three times for each guinea pig, prior to intratympanic injection, on the tenth and twenty-first days after the injections. Wilcoxon Signed Ranks Test, Mann ? Whitney U Test and Kruskal ? Wallis Test were used for statistical analysis of data.Results: In Groups 1 and 2, following Castellani and gentamicin injections, distortion product otoacoustic emissions were absent on tenth and twenty-first days of the experiment. However, for Group 3, there was no significant change in both responses for the same time periods. The only statistical difference was occurred between the auditory evoked brainstem potential thresholds before and after the twenty-first day of the experiment of the saline solution. On the tenth and twenty-first day of the experiment, in the ears belong to Groups 1 and 2, auditory evoked brainstem potentials thresholds were found to be significantly increased, whereas in Group 3 ears any threshold shifts obtained were 5 dB HL only. Thus, the latter result is not considered to be due to ototoxicity. According to statistical analysis, significant differences were found between Groups 1 and 3 as well as Groups 2 and 3.Conclusion: It is concluded that Castellani?s solution has ototoxic effect on guinea pigs. Thus, Castellani?s solution is not to be recommended to patients with tympanic membrane perforation. As a further research, all the components of Castellani?s solution should be tested individually.Key words: Ototoxicity, Castellani?s solution, gentamicin, otomycosis, ototopical agents.