The pharmacokinetics of florfenicol were studied in both healthy (n=9) and Escherichia coli-infected (n=27) broiler chickens following intravenous (i.v.), intramuscular (i.m.) and oral administration at a single dose of 30 mg/kgbw. Infection was induced artificially in broiler chickens (35 d) by an intraperitoneal injection with 1.3 x 10(9) colony-forming units of E. coli. After i.v. administration in healthy and infected broiler chickens, the disposition kinetics of florfenicol were described by a bi-exponential equation. In diseased broiler chickens, a decrease in the elimination half-life and the apparent volume of distribution were found. The pharmacokinetic parameters such as total body clearance and the areas under curves of plasma concentrations were comparable in healthy and E. coli infected chickens. Following i.m. and oral administration in infected chickens, the plasma concentration-time data for florfenicol were found to fit a single-compartment open model. The elimination half-lives (t(1/2 el)) of florfenicol were 129(13) and 104(15)min, the systemic bioavailability 87% and 71% after i.m. and oral administration.