Influence of acute renal impairment in the penetration of cefoxitin into interstitial tissue fluid in rabbits.

The pharmacokinetics of cefoxitin were studied after the administration of a single intravenous dose of 40 mg/kg to rabbits with normal renal function and rabbits with varying degrees of renal impairment. The plasma and interstitial fluid concentrations of the antibiotic were determined by a microbiologic plate diffusion method. The antibiotic follows a two-compartment open kinetic model. The plasma half-life of slow disposition phase t1/2 beta, increases from 0.26 hour in rabbits with normal renal function to 5.41 hours in rabbits with severe renal impairment. In the interstitial fluid the elimination half-life increases from 1.18 hours in rabbits with normal renal function to 99.00 hours in rabbits with renal impairment. A linear relationship is established between the values that define the elimination of the antibiotic and the serum creatinine concentrations. The constant of the incorporation into the interstitial fluid decreases significantly in rabbits with renal impairment.