THE PHARMACOKINETICS OF SALICYLATE IN DAIRY-CATTLE ARE NOT ALTERED BYSIMULTANEOUS INTRAVENOUS CEFTIOFUR SODIUM AND DL-LYSINE-ACETYL SALICYLATE (ASPIRIN)

This study evaluated potential alterations to the pharmacokinetics of salicylate by concurrently administered ceftiofur sodium. The trial de sign was a crossover using 10 non-lactating, non-pregnant dairy cows. In the first period each cow received intravenously (IV) 26 mg/kg of D L-lysine acetyl salicylate (aspirin) followed immediately by 2 mg/kg c eftiofur sodium. In the second period each cow received 26 mg/kg of as pirin IV. Plasma samples were harvested for determination of salicylat e concentration by HPLC. The data best fitted a single compartment ope n model, using weighted non-linear regression. No alterations to the p harmacokinetic parameters of salicylate in cattle by concurrently admi nistered ceftiofur sodium were detected (P < 0.05), Using 90% confiden ce intervals, and testing for changes of > 20%, control values, elimin ation half-life (t(1/2)), apparent volume of distribution (V-d), area under the plasma concentration versus time curve (AUG) and mean reside nce time (MRT) were not altered. For control animals the elimination r ate constant (k(el)) and total body clearance (CI) were 1.35+/-0.43 h( -1) and 20.2+/-6.1 ml/h . kg respectively (mean+/-SD). Since ceftiofur sodium did not affect the pharmacokinetics of salicylate, dose regime ns for aspirin in cattle need not be altered when ceftiofur sodium is administered concurrently.