Occurrence and risk of cochleotoxicity in cystic fibrosis patients receiving repeated high-dose aminoglycoside therapy

Cystic fibrosis (CF) patients receive repeated courses of aminoglycoside th erapy. These patients would consequently be expected to be more susceptible to cochleotoxicity, a recognized side effect with single courses of aminog lycoside therapy. The primary aim of this retrospective study was to establ ish the incidence and severity of auditory deficit in CF patients. Standard (0.25- to 8-kHz) and high-frequency (10- to 16-kHz) pure-tone audiometry w as carried out in 70 CF patients, and the results were compared with the re sults from 91 control subjects. These subjects were further divided into pe diatric and adult groups. Of 70 CF patients, 12 (1 pediatric) displayed hea ring loss considered to be caused by repeated exposure to aminoglycosides. There was a nonlinear relationship between the courses of therapy received and the incidence of hearing loss. The severity of the loss did not appear to be related to the number of courses received. Assuming the risk of loss to be independent for each course, preliminary estimates of per course risk of hearing loss were less than 2%. Upon comparison with previous clinical studies and experimental work, these findings suggest that the incidence of cochleotoxicity in CF patients is considerably lower than would be expecte d, suggesting that the CF condition may confer protection against aminoglyc oside cochleotoxicity.