The occurrence of flunixin residues in bovine milk samples from the United States

Flunixin (FLU) is a non-steroidal anti-inflammatory drug (NSAID) approved in the United States for use in beef and dairy cattle for modulation of inflammation in endotoxemia and for the control of pyrexia associated with bovine respiratory disease and acute bovine mastitis. FLU is labeled for intravenous administration at a dose of 2.2 mg/kg every 24 hours or 0.5 mg/lb (1.1 mg/kg) every 12 hours for up to 3 days. The slaughter withdrawal time is 4 days following the last injection and the milk withdrawal time is 36 hours. Since 2005, the United States Department of Agriculture-Food Safety Inspection Service (USDA-FSIS) has reported an increasing number of residue violations in meat from dairy cattle (USDA-FSIS, 2005-2010). This increase in the number of FLU residue violations has led to FLU becoming the second most common residue violation behind penicillin in cull dairy cattle (USDA-FSIS). In milk the marker residue is a metabolite of FLU, called 5-hydroxy flunixin (50H) and the tolerance for 50H in milk is 2 ppb. Milk samples in the United States are not routinely tested for 50H (National Milk Drug Residue Data Base Fiscal Year 2011 Annual Report). However, due to the significant number of FLU tissue residues violations found in cull dairy cows, there is concern that the same practices which have led to tissue residues may also lead to drug residues in milk.