Serial studies of auditory neurotoxicity in patients receiving deferoxamine therapy

Visual and auditory neurotoxicity was previously documented in 42 of 89 patients with transfusion-dependent anemia who were receiving iron chelation therapy with daily subcutaneous deferoxamine. Twenty-two patients in the affected group had abnormal audiograms with deficits mostly in the high frequency range of 4,000 to 8,000 Hz and in the hearing threshold levels of 30 to 100 decibels. When deferoxamine therapy was discontinued and serial studies were performed, audiograms in seven cases reverted to normal or near normal within two to three weeks, and nine of 13 patients with symptoms became asymptomatic. Audiograms from 15 patients remained abnormal and four patients required hearing aids because of permanent disability. Since 18 of the 22 patients were initially receiving deferoxamine doses in excess of the commonly recommended 50 mg/kg per dose, therapy was restarted with lower doses, usually 50 mg/kg per dose or less depending on the degree of auditory abnormality, and with the exception of two cases no further toxicity was demonstrated. Auditory deterioration and improvement, demonstrated serially in individual patients receiving and not receiving deferoxamine, respectively, provided convincing evidence for a cause-and-effect relation between deferoxamine administration and ototoxicity. Based on these data, a plan of management was developed that allows effective yet safe administration of deferoxamine. A dose of 50 mg/kg is recommended in those without audiogram abnormalities. With mild toxicity, a reduction to 30 or 40 mg/kg per dose should result in a reversal of the abnormal results to normal within four weeks. Moderate abnormalities require a reduction of deferoxamine to 25 mg/kg per dose with careful monitoring. In those with symptoms of hearing loss, the drug should be stopped for four weeks, and when the audiogram is stable or improved, therapy should be restarted at 10 to 25 mg/kg per dose. Serial audiograms should be performed every six months in those without problems and more frequently in young patients with normal serum ferritin values and in those with auditory dysfunction.