The effect of phenylbutazone on the plasma disposition of penicillin G in the horse

An integrated experimental and physiologically based pharmacokinetic modeling study of penicillin G in heavy sows

Penicillin G is widely used in food-producing animals at extralabel doses and is one of the most frequently identified violative drug residues in animal-derived food products. In this study, the plasma pharmacokinetics and tissue residue depletion of penicillin G in heavy sows after repeated intramuscular administrations at label (6.5 mg/kg) and 5 × label (32.5 mg/kg) doses were determined. Plasma, urine, and environmental samples were tested as potential antemortem markers for penicillin G residues. The collected new data and other available data from the literature were used to develop a population physiologically based pharmacokinetic (PBPK) model for penicillin G in heavy sows. The results showed that antemortem testing of urine provided potential correlation with tissue residue levels. Based on the United States Department of Agriculture Food Safety and Inspection Service action limit of 25 ng/g, the model estimated a withdrawal interval of 38 days for penicillin G in heavy sows after 3 repeated intramuscular injections at 5 × label dose. This study improves our understanding of penicillin G pharmacokinetics and tissue residue depletion in heavy sows and provides a tool to predict proper withdrawal intervals after extralabel use of penicillin G in heavy sows, thereby helping safety assessment of sow-derived meat products.

Pharmacokinetics of oleandomycin in dogs after intravenous or oral administration alone and after pretreatment with metamizole or dexamethasone

The pharmacokinetics of oleandomycin (OLD) after intravenous and oral administration, both alone and after intramuscular pretreatment with metamizole or dexamethasone, were studied in healthy dogs. After intravenous injection of OLD alone (10 mg/kg as bolus), the elimination half-life (t 1/2 beta, volume of distribution (Vd,area), body clearance (ClB) and area under the concentration time curve (AUC) were 1.60 h, 1.11 L/kg. 7.36 (ml/kg)/min and 21.66 microg h/ml, respectively. There were no statistically significant differences following pretreatment with metamizole or dexamethasone. After oral administration of OLD alone, the t 1/2 beta, maximum plasma concentrations (Cmax), time of Cmax (tmax), mean absorption time (MAT) and absolute bioavailability (Fabs) were 1.6 h, 5.34 microg/ml, 1.5 h, 1.34 h and 84.29%, respectively. Pretreatment with metamizole caused a significantly decreased value for Cmax (2.93 microg/ml) but the MAT value (2.23 h) was significantly increased. Statistically significant changes in the pharmacokinetic parameters of OLD following oral administration were also observed as a result of pretreatment with dexamethasone. The Cmax was increased (8.24 microg/ml) and the tmax (0.5 h) and MAT (0.45 h) were lower.