The effects of deferoxamine mesylate and hypoxia on the cochlea.

Deferoxamine mesylate (DF) is a chelating agent used for the treatment of iron overload. Recently audiological testing of patients on long-term treatment with this drug indicated the possibility of an ototoxic side effect (1). We administered DF to chinchillas with both acute and chronic regimes. Functional and histological damage to the cochlea was detected only in the acute experiment. This was assumed to come not from the direct effect of DF on the cochlea but from the hypoxia as a result of respiratory suppression due to DF toxicity. To confirm this, animals were exposed to hypoxia during the same time course as for the DF experiment. Histological and physiological consequences of this hypoxia alone revealed very similar results to that observed in the acute DF experiment. This implies that DF has little direct toxic effect on the cochlea and, more importantly that considerable attention to hypoxia should be paid when assessing the cochlear pathology of animals which have been subjected to general anesthesia for long periods.