Cisplatin-Induced Ototoxicity and the Effects of Intratympanic Diltiazem in a Mouse Model

Objective To evaluate whether the calcium-channel blocker diltiazem has protective effects against cisplatin-induced ototoxicity in a mouse model. Study Design Original basic science in vivo investigation. Setting Academic setting: Otolaryngology-Head and Neck Surgery laboratory at University of Connecticut Health Center. Subjects Thirty-nine female CBA/J mice. Methods Pure tone- or click-evoked auditory brainstem responses (ABRs) were recorded in CBA/J mice to determine auditory thresholds. All mice had baseline ABRs recorded. They were then given a single cisplatin bolus (14 mg/kg), followed by 5 consecutive days of intratympanic diltiazem or saline control. Follow-up thresholds were recorded on days 7, 14, and 21 postcisplatin. Tone-evoked ABRs evaluated the otoprotective effect of 2-mg/kg diltiazem in 9 mice, and dose effect was examined in response to click-evoked ABR with 2- or 4-mg/kg diltiazem in 2 groups of 15 mice. Results Saline-treated ears had significantly elevated tone-evoked auditory thresholds when compared with diltiazem-treated ears (P = .038) on day 7 postcisplatin only. Click-evoked ABR thresholds were significantly elevated in saline-treated ears versus diltiazem-treated ears for the 2-mg/kg group (P = .001) and 4-mg/kg group (P = .011) on days 7, 14, and 21 postcisplatin. Conclusion Intratympanic diltiazem has significant protective effects against cisplatin ototoxicity at 2 and 4 mg/kg. This is the first in vivo study to demonstrate that diltiazem offers a potentially novel therapy for cisplatin-induced ototoxicity.