Does Calcium Dobesilate Have Therapeutic Effect on Gentamicin-induced Cochlear Nerve Ototoxicity? An Experimental Study

Hypothesis: The ototoxic effects of aminoglycosides are well known. Gentamicin carries a substantial risk of hearing loss. Gentamicin is widely used to combat life-threatening infections, despite its ototoxic effects. Calcium dobesilate is a pharmacologically active agent used to treat many disorders due to its vasoprotective and antioxidant effects. We investigated the therapeutic role of calcium dobesilate against gentamicin-induced cochlear nerve ototoxicity in an animal model. Methods: Thirty-two Sprague Dawley rats were divided into four groups: Gentamicin, Gentamicin + Calcium Dobesilate, Calcium Dobesilate, and Control. Preoperative and postoperative hearing thresholds were determined using auditory brainstem response thresholds with click and 16-kHz tone-burst stimuli. Histological analysis of the tympanic bulla specimens was performed under light and transmission electron microscopy. The histological findings were subjected to semiquantitative grading, of which the results were compared between the groups. Results: Gentamicin + Calcium Dobesilate group had, on average, 27 dB better click-evoked hearing than Gentamicin group ( p < 0.01), whereas the difference was not significant with 16-kHz tone-burst stimuli ( p > 0.01). Histologically examining the Control and Calcium Dobesilate groups revealed normal ultrastructural appearances. The Gentamicin group showed the most severe histological alterations including myelin destruction, total axonal degeneration, and edema. The histological evidence of damage was significantly reduced in the Gentamicin + Calcium Dobesilate group compared with the Gentamicin group. Conclusion: Adding oral calcium dobesilate to systemic gentamicin was demonstrated to exert beneficial effects on click-evoked hearing thresholds, as supported by the histological findings.