Pharmacokinetics and milk elimination of flunixin meglumine in dairy cattle following different routes of administration

Abstract

Flunixin meglumine (FLU) is a non-steroidal anti-inflammatory licensed for use in dairy cattle for treatment of inflammation in endotoxemia and control of pyrexia associated with bovine respiratory disease and acute bovine mastitis. FLU is labeled for intravenous (IV) administration at a dose of 1 mg/lb (2.2 mg/kg) every 24 hours or 0.5 mg/lb (1.1 mg/kg) every 12 hours. The milk withdrawal time is 36 hours. Currently, FLU is the second most common violative drug residue found in the dairy industry. The reason for the numerous illegal FLU drug residues remains unclear; however, administration by an unapproved route is one possible explanation. The administration of FLU by intramuscular (IM) or subcutaneous (SC) routes may prolong drug elimination and result in milk concentrations of the metabolite, 5-hydroxy flunixin (5OH), the marker residue for milk, to exceed the tolerance level of 2 ppb for > 36 hours. The objective of this study was to determine if the pharmacokinetics and milk residues of FLU and 5OH in lactating dairy cattle differed following IM and SC administration of FLU, compared with those following IV administration of FLU.