The pharmacokinetics of salicylate in dairy cattle are not altered by simultaneous 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 design was a crossover using 10 non-lactating, non-pregnant dairy cows. In the first period each cow received intravenously (IV) 26 mg/kg of DL-lysine acetyl salicylate (aspirin) followed immediately by 2 mg/kg ceftiofur sodium. In the second period each cow received 26 mg/kg of aspirin IV. Plasma samples were harvested for determination of salicylate concentration by HPLC. The data best fitted a single compartment open model, using weighted non-linear regression. No alterations to the pharmacokinetic parameters of salicylate in cattle by concurrently administered ceftiofur sodium were detected ( P <0.05). Using 90% confidence intervals, and testing for changes of > 20%. control values, elimination half-life ( t ₁/₂), apparent volume of distribution ( V _d), area under the plasma concentration versus time curve ( AUC ) and mean residence time ( MRT ) were not altered. For control animals the elimination rate constant ( k _el) and total body clearance ( Cl ) were 1.35/pm0.43 h⁻¹ and 20.2/pm6.1 ml/h.kg respectively (mean/pmSD). Since ceftiofur sodium did not affect the pharmacokinetics of salicylate, dose regimens for aspirin in cattle need not be altered when ceftiofur sodium is administered concurrently.