The Effects of Memantine on Cisplatin-induced Ototoxicity.

Introduction: We aimed to investigate electrophysiologically and histopathologically, the protective effects of intratympanic memantine, an N-methyl-D-aspartate receptor antagonist, on ototoxicity caused by cisplatin, an anti-neoplastic agent used in many types of cancer.

Methods: Thirty-seven guinea pigs with a normal auditory function were randomly allocated to group 1 (Cisplatin; n=8), group 2 (Memantine; n=8), group 3 (Cisplatin+Memantine; n=8), group 4 (Cisplatin+Physiological Serum [PS]; n=8), and group 5 (Control; n=5). Auditory assessments were conducted using distortion product otoacoustic emissions (DPOAE) within a frequency range of 1-32 kHz, and auditory brainstem responses (ABR) within 8-32 kHz. A single dose of cisplatin (12 mg/kg) was administered intraperitoneally, followed by intratympanic administration of 0.2 mL of either memantine or PS to both ears at least half an hour before cisplatin administration. Subsequent auditory evaluations were conducted 72 h after cisplatin administration. Histopathological analyses were performed using light microscopy of the right ear and scanning electron microscopy (SEM) of the left ear.

Results: Auditory evaluations conducted before and after treatment revealed significant findings. Specifically, within groups 3 and 4, ABR thresholds were elevated at all frequencies (p=0.00), whereas the DPOAE signal-to-noise ratios were reduced at frequencies of 8, 12, 16, and 24 kHz (p=0.001, p=0.01, p=0.01, and p=0.00, respectively). Histopathologically, both light microscopy and SEM revealed that the cisplatin+memantine group exhibited fewer hair cells and nuclear degeneration in the spiral ganglion than the cisplatin and cisplatin+PS groups. Additionally, the stria vascularis thickness was greater in the cisplatin+memantine group than in cisplatin and cisplatin+PS groups.

Conclusion: Despite the negative electrophysiological findings, the histopathological outcomes suggest that intratympanic memantine may have a potential protective effect against cisplatin-induced ototoxicity. However, further investigations are warranted to corroborate these findings and elucidate the underlying mechanisms of action of memantine.