Ototoxicity caused by aminoglycosides is ameliorated by melatonin without interfering with the antibiotic capacity of the drugs

The production of free radicals seems to be involved in the mechanisms of o totoxicity. Aminoglycosides produce ototoxicity, which can be determined th rough distortion product otoacoustic emissions (OAEs) that measure the acti vity of the outer hair cells of the organ of Corti. An ototoxic chart was o btained in rats using gentamicin or tobramycin. Together with this treatmen t, the animals ingested melatonin in the drinking water, or melatonin was i njected subcutaneously or intramuscularly. The distortion product OAEs were determined over a prolonged period of time for each of the groups. The eff ect of melatonin on the antibiotic capacity of the aminoglycosides used was also studied. Antibiograms inoculated with Escherichia toll or Pseudomonas aeruginosa and treated with gentamicin or tobramycin in the presence or ab sence of melatonin at quantities from pharmacological to physiological dose s were performed. The ototoxicity produced by gentamicin and tobramycin was maximal from days 3 to 5 post-treatment, returning to normal values in 2 w k. When melatonin was present, the recovery was at day 5 post-treatment, in dependently of the means of administration of the pineal product. The antib iograms showed that melatonin had no effect on the antibiotic capacity. It is concluded that the ototoxicity caused by gentamicin and tobramycin is am eliorated by melatonin and that the pineal hormone does not interfere with the antibiotic capacity of these antibiotics.