Comparison of the nephrotoxicity and auditory toxicity of tobramycin and amikacin

A total of 157 patients were treated with tobramycin or amikacin in a controlled prospective randomized trial. Dosages were adjusted to renal function according to a nomogram. Trough and peak aminoglycoside levels were available at the end of the trial. Of the above total, 113 recipients of nine or more doses of tobramycin or six or more doses of amikacin, without other apparent cause of renal failure, were evaluated for nephrotoxicity. Thirty-six patients were evaluated for auditory toxicity. The patients in groups evaluated for either nephrotoxicity or auditory toxicity were similar with respect to intensity and etiology of bacterial disease, concurrent exposure to other antimicrobial drugs, age and sex distribution, initial serum creatinine level, and total dose and duration of antimicrobial therapy. Nephrotoxicity of similar severity developed in 4 of 59 (6.8%) recipients of tobramycin and in 7 of 54 (13.1%) recipients of amikacin (P greater than 0.05). Mild auditory toxicity developed in 3 of 19 (15.7%) recipients of tobramycin and in 2 of 17 (11.7%) recipients of amikacin (P greater than 0.05). When patients with abnormally high mean trough or peak aminoglycoside levels were excluded from comparison, nephrotoxicity was 6.12 and 5.12% (P greater than 0.05) and auditory toxicity was 17.6 and 7.69% (P greater than 0.05) in the groups given tobramycin and amikacin, respectively. We conclude that the nephrotoxicity and auditory toxicity of amikacin and tobramycin are not significantly different and that such toxicities are indeed infrequent events when the dosages of these drugs are adjusted to hold blood levels within the safe boundaries suggested by the studies of others.