Quantitative nephrotoxicity of gentamicin in nontoxic doses.

The effect of gentamicin on the renal function of 36 patients was studied by means of several techniques. After normal or even subnormal doses of gentamicin, progressively decreasing rates of glomerular filtration, as measured by clearance of [51Cr]ethylenediaminetetracetic acid, were observed in a majority of the patients, although trough and peak concentrations in serum were well below accepted levels of gentamicin toxocity. Correspondingly, the serum half-lives of gentamicin tended to increase during the courses of treatment. Changes in levels of serum creatinine were not pronounced enough to demonstrate the decreasing rates of glomerular filtration. Studies on serum and urinary levels of a low-molecular-weight protein, beta2-microglobulin, indicated that gentamicin affects the kidney both on the glomerular and the tubular level. The results emphasized the need for monitoring of gentamicin dosages as well as the need for alternative antibiotics to treat patients with preexisting renal impairment.