Pharmacokinetics of tobramycin in rats with reduced renal parenchyma and in experimental shock.

Ten days after four-fifths nephrectomy in rats (four-fifths of the renal parenchyma removed), the total and renal elimination constants of tobramycin were lowered by one-half. The biological half-life of tobramycin doubled. These results suggest that soon after nephrectomy the residual nephrons are able to increase the rate of excretion of tobramycin. The increase in mass of the remaining renal tissue between day 10 and day 80 after nephrectomy had no effect on the biological half-life, on the total and renal elimination constants, and on the renal clearance of tobramycin. During endotoxin shock and burn shock, concentrations of tobramycin in serum decreased at a slower rate. The highest serum concentrations of tobramycin were observed in rats with shock due to burns.