Influence of Escherichia coli endotoxin induced fever on the pharmacokinetics and dosage regimen of oxytetracycline in cross-bred calves.

The pharmacokinetics and dosage regimen of oxytetracycline were determined in healthy and febrile cross-bred calves following its single intravenous administration (10 mg kg-1). Fever was induced by a single intravenous injection of E. coli endotoxin (1 microgram kg-1 i.v.). The elimination half-life (t1/2 beta) and the apparent volume of distribution [vd(area)] were slightly increased in febrile calves, as compared to healthy animals. The values of t1/2 beta and Vd(area) were 3.22 +/- 0.20 h and 0.49 +/- 0.02 L. kg-1 in healthy calves and 4.06 +/- 0.32 h and 0.70 +/- 0.09 L kg-1, respectively, in febrile calves. An intravenous dosage regimen suitable for maintaining the minimum therapeutic plasma concentration of > or = 2 micrograms/ml in febrile animals would be 10 mg kg-1 repeated at 12-h intervals.