PHARMACOKINETICS OF PENICILLIN-G IN EWES AND COWS IN LATE PREGNANCY AND IN EARLY LACTATION

Concentrations of penicillin-G in serum were determined after single i ntravenous doses of potassium penicillin-G (10 mg/kg body wt) to ewes and cows in late pregnancy and in early lactation, Penicillin-G in ser um was analysed by a microbiological method and pharmacokinetic parame ters were calculated by model-independent methods, Serum concentration s were lower in early lactation than in late pregnancy in both ewes an d cows, The differences were statistically significant at most samplin g times in ewes but only during the first hour in cows. Weight correct ed values of clearance and volume of distribution were significantly h igher in early lactation than in late pregnancy in both ewes and cows. Mean residence time and elimination-half life were shorter in lactati ng than in pregnant ewes, however for the latter parameter the differe nce was not statistically significant. Neither of these parameters cha nged in cows. It is concluded that in both ewes and cows pharmacokinet ic parameters of penicillin-G are altered from late pregnancy to early lactation but that these changes have little practical impact and do not call for a revised dosage regime of the studied drug.