CHLORAMPHENICOL PHARMACOKINETICS AFTER INTRAVENOUS AND INTRAMUSCULAR ADMINISTRATION IN SHEEP

The pharmacokinetics of chloramphenicol were studied after intravenous and intramuscular administration of 50 mg/kg body weight in Merino sh eep. After intravenous administration, the drug was rapidly distribute d extravascularly with a half-life of 10.5 +/- 8.83 min. Extensive dis tribution was confirmed by an apparent volume of distribution at stead y state (1.5 +/- 0.43 l/kg). The elimination half-life was 3.24 +/- 0. 60 h. After intramuscular injection, the absorption half-life was 44.3 3 +/- 19.21 min with a bioavailability of 65 %. A maximum serum concen tration of 15.57 +/- 3.95 mu g/ml was determined 2 h after administrat ion. Serum concentrations above 5 mu g/ml were maintained for approxim ately 12 h with an elimination half-life of 5.75 +/- 1.25 h, longer th an the half-life obtained after intravenous administration. In conclus ion, the intramuscular administration of chloramphenical at a dose rat e of 50 mg/kg permitted the maintenance of inhibitory concentrations o f the antibiotic for the majority of Salmonella and Pasteurella isolat es for at least 12 h.