Comparative tissue accumulation of gentamicin and tobramycin in patients

We studied the comparative multiple-dose pharmacokinetics of gentamicin and tobramycin in a group of 82 patients (47 gentamicin, 35 tobramycin) who did not experience nephrotoxicity. A. 2-compartment model was used to predict the amount of gentamicin or tobramycin in the tissues, and these predictions were in good agreement with drug recovery from urine or postmortem tissue (r = 0·96, P`0·01). The 2 groups of patients were not different clinically, but patients receiving gentamicin had higher serum levels, a smaller central volume of distribution, and lower body clearance than those on tobramycin. Comparison of predicted tissue accumulation revealed that tobramycin had significantly less (P `0·05) accumulation in these patients, even after patients were matched to control for differences in renal function, terminal half-life, and dose. These studies raise the possibility that the use of tobramycin may be associated with less nephrotoxicity.