Pharmacokinetics of chloramphenicol in non‐lactating cattle

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Abstract
The pharmacokinetics and bioavailability of a formulation of chloramphenicol base in propylene glycol were determined following administration of single i.v. and s.c. 50 mg/kg doses of chloramphenicol to 6 non-lactating Holstein cows. Mean serum concentrations of chloramphenicol following i.v. administration of 50 mg/kg declined rapidly from a peak of greater than 100 .mu.g/ml to 6.9 .mu.g/ml at 12 h after administration. Serum concentrations were not detectable at 24 h after administration. The curve of serum concentrations vs. time was characteristic of a 2-compartment open model. Mean i.v. data gave a biological half-life [t1/2] of 4.3 h and a volume of distribution of the central compartment of 0.44 l/kg. Serum concentrations of chloramphenicol following s.c. administration of 50 mg/kg rose slowly to a broad peak near 20 .mu.g/ml from 3-8 h after administration and then declined. These data were also analyzed according to a 2-compartment open model. The biological t1/2 was 4.2 h and the volume of distribution of the central compartment was 0.50 l/kg. Significant adverse reactions, including acute collapse, intravascular hemolysis and hemoglobinuria, were observed in cows when dosed i.v. Cows dosed s.c. exhibited local reactions at injection sites. The disadvantages of administration of 50 mg/kg doses of chloramphenicol base in propylene glycol appear to be significant and may outweigh the potential advantages of parenteral use of the drug as presently formulated.