Effect of melatonin on otoprotection: A systematic review with metaanalysis
melatonin, rodents, ototoxic agents, otoprotection
Melatonin is a promising antioxidant substance that can minimize the effects of ototoxicity-induced hearing loss. Experimental studies have been performed to test the otoprotective efficacy of melatonin. Objective: To analyze the methodology presented by primary studies on determining the otoprotective efficacy of melatonin. The study is a systematic review with meta-analysis to clarify if the hormone is promising in preventing/minimizing human ototoxicity. Methods: Altogether, 154 articles were found in four databases. The PICOS strategy (Population, Intervention, Comparison, and Outcome) was used to define the eligibility criteria. Studies that met the inclusion criteria for the second step were included in a qualitative synthesis. Each study type was analyzed with the Critical Appraisal Checklist for Quasi-experimental Studies and the Critical Appraisal Checklist for Randomized Controlled Trials of the Joanna Briggs Institute. Results: Seven articles were selected, and four were included in the meta-analysis. It was possible to obtain seven outcomes according to the standard auditory frequencies presented among the studies, considering a minimum of three standard frequencies. The outcomes analyzed were for the frequencies of 1500, 2000, 3000, 4000, 5000, 6000, and 8000 Hz. Conclusion: Melatonin can provide protection against the ototoxic effects of cisplatin and aminoglycosides at 5000 Hz, 6000 Hz, and 8000 Hz, thereby minimizing the reduction in Otoacustic Emissions (OAE) amplitude. The same effect was not observed in the lower frequencies. Despite the limited number of studies that were evaluated, the results appeared consistent in higher frequencies. However, the methodology of the available studies did not meet the necessary methodological rigor that promotes the safe replicability of these studies.