Pharmacokinetics of ibuprofen in lactating dairy cows.

The pharmacokinetics of ibuprofen were studied in 6 adult lactating dairy cows after a single IV or oral administration of ibuprofen (25 mg/kg of body weight). Ibuprofen concentrations in milk and serum were analyzed by use of high-performance liquid chromatography. The lower limit of detection of the ibuprofen assay was 50 ng/ml. Serum ibuprofen concentration-time curves after IV administration best fit an open two-compartment model. Harmonic mean volume of distribution at steady state was 0.14 (range, 0.12 to 0.17) L/kg, elimination half-life was 1.55 (range, 1.33 to 1.73) hours, and total clearance was 86.2 (range, 68.8 to 106.2) ml/kg/h. Harmonic mean oral bioavailability was 99% (range, 79 to 112). Adverse effects were not observed in cows given ibuprofen.