Effect of Folic Acid on Cisplatin-Induced Ototoxicity: A Functional and Morphological Study

OBJECTIVES: The aim of our study was to investigate the effects of folic acid on cisplatin-induced ototoxicity. MATERIALS AND METHODS: Thirty Wistar albino rats were divided into five groups. Group I received intraperitoneal cisplatin (IP) 10 mg/kg/day and IP folic acid 10 mg/kg/day; Group II received IP cisplatin 10 mg/kg/day and IP physiological saline; Group III received IP cisplatin 10 mg/kg/day and intratympanic (IT) folic acid 0.15 mL/day; Group IV received IP cisplatin 10 mg/kg/day and IT physiological saline; and Group V received IT folic acid 0.15 mL/day. Before and after drug administration, plasma homocysteine, folic acid levels, and auditory brainstem evoked responses (ABR) were measured. The rats were then sacrificed, and the inner ears were processed for electron microscopy. RESULTS: The differences of ABR thresholds in Group I compared to Group II were significantly smaller at 4 kHz, 8 kHz, and 16 kHz, whereas they were smaller but not statistically significant at 12 kHz in ABR. The differences of ABR thresholds in Group III compared to Group IV were significantly smaller at 12 kHz, and smaller but not statistically significant at 4 kHz, 8 kHz, and 16 kHz. Cisplatin treatment resulted in the degeneration of the cells of the organ of Corti, stria vascularis, and spiral ganglion. The cells of the organ of Corti, stria vascularis, and spiral ganglion showed a partially preserved morphology in both Group I and Group III. CONCLUSION: Our study results suggests that folic acid is a potential agent in preventing cisplatin-induced ototoxicity.