THIAMPHENICOL PHARMACOKINETICS IN BEEF AND DAIRY-CATTLE

The pharmacokinetics of thiamphenicol were investigated in 10 calves a nd six lactating cows. It was found that this drug is rapidly absorbed (15 min) following intramuscular injection with an absorption rate co nstant and a bioavailability of 8.7 h-1 and 84%, respectively. The dru g appears to be widely distributed into various body fluids, yielding a volume of distribution (V(d)(area)) of approximately 0.9 l/kg. The m icro-rate constants indicated that the antibiotic rapidly diffuses int o the peripheral compartment (k12 > k21). Elimination from plasma is r elatively rapid, with a biological half-life of about 1.75 h. Thiamphe nicol appears shortly in milk (15 min) after its intravenous administr ation, and gives milk to plasma concentration ratios greater than one between 4 and 12 h.