Comparison of Nephrotoxicity of Tobramycin and Gentamicin

To the Editor.— The prospective study of the clinical nephrotoxicity of tobramycin sulfate and gentamicin sulfate reported by Gerald D. Kumin, MD (1980;244:1808), brings further attention to the magnitude of the problem of aminoglycoside-related renal failure and presents data indicative of a substantially higher incidence of gentamicin-associated renal dysfunction in comparison with that of tobramycin in groups receiving standard clinical daily doses of these drugs. However, despite the admission of the difficulty in designing controlled clinical studies in seriously ill patients, 62 patients were treated with 2 to 5 mg/kg/day of gentamicin sulfate or tobramycin sulfate for a variety of serious infections. No serum aminoglycoside levels are reported, and no data are presented to allow conclusions regarding possible differences in efficacy of therapy between groups. Yet there is another issue. Riff and Jackson 1 demonstrated that the dosage of gentamicin based on the weight of the patient produced wide variations