Pharmacokinetics, intramuscular bioavailability and tissue residue profiles of ceftazidime in a rabbit model

This study investigated the disposition kinetics and plasma availability of ceftazidime in rabbits after single intravenous (iv) and intramuscular (im ) injections of 50 mg kg(-1) b.wt. Tissue residue profiles were studied aft er repeated intramuscular injections of 50mg kg(-1) b. wt, twice daily for five consecutive days. A microbiological assay with Bacillus subtilis as th e test organism was used to measure its concentrations in plasma and tissue s,The plasma concentration-vs-time curves were best described by a two comp artment open model, The decline in plasma drug concentration was biexponent ial with half-lives of 0.258 h for t(1/2 alpha), 2.22 h for t(1/2 beta), fo r distribution and elimination phases, respectively following iv injection. After intramuscular injection of ceftazidime at the same dose, it was dete cted in plasma at 5 min and reached its minimum level 12 h pest-injection. The peak plasma concentration (C-max) 66.3 mug (.) ml(-1) was attained at 0 .779 h (T-max). The elimination half-life (T-1/2e) was 2.12 h, the mean res idence time (MRT) was 3.06 h and the systemic bioavailability was 96.6 %. I n vitro protein binding percent of ceftazidime in rabbit's plasma was range d from 13.3 to 21.6 %. The limit of quantification (LOQ) for the assay was 0.01 mug (.) ml(-1) in plasma and tissues. The tissue level concentrations were highest in the kidneys, and decreased in the following order: liver > heart > muscles and plasma. No ceftazidime residues were detested in tissue s and plasma after 72 h, It is concluded that tissue kinetics is an importa nt tool in predicting and controlling drug residues in edible tissues of fo od producing animal.