The comparative pharmacokinetics of ceftazidime and cefotaxime in healthy volunteers.

The pharmacokinetic behaviour of two aminothiazolyl cephalosporins, ceftazidime (CAZ) and cefotaxime (CTX), were compared in three studies. Doses of each antibiotic were given intravenously (500 mg, n=4; 1 g, n=4) or intramuscularly (1 g, n=8) in a cross-over manner to healthy male volunteers. Antibiotic assays were performed by HPLC and microbiological assay techniques. Both antibiotics appeared to fit a two-compartment iv kinetic model with terminal half-lives of 1.7 h (CAZ) and 0.8 h (CTX). CAZ was metabolically stable whereas there was 34% conversion of CTX to desacetyl-CTX. The 24 h urinary recovery of CAZ averaged 89% but only 51% for CTX. The protein binding of CAZ was 17% and of CTX was 47%. CTX was more painful than CAZ on im injection in seven of the eight volunteers. CAZ therefore appeared to possess a number of features more favourable than those of CTX, when assessed in healthy volunteers.