Update on the use of cyclooxygenase-2-selective nonsteroidal anti-inflammatory drugs in horses.

Nonsteroidal anti-inflammatory drugs work through inhibition of cyclooxygenase (COX) and are highly effective for the treatment of pain and inflammation in horses. There are 2 clinically relevant isoforms of COX. Cyclooxygenase-1 is constitutively expressed and is considered important for a variety of physiologic functions, including gastrointestinal homeostasis. Thus, NSAIDs that selectively inhibit COX-2 while sparing COX-1 may be associated with a lower incidence of adverse gastrointestinal effects. Various formulations of firocoxib, a COX-2-selective NSAID, labeled for use in horses are available in the United States. Equine practitioners should know that the FDA limits the use of firocoxib to formulations labeled for horses, regardless of price concerns. In addition, practitioners will benefit from understanding the nuances of firocoxib administration, including the importance of correct dosing and the contraindications of combining NSAIDs. Together with knowledge of the potential advantages of COX-2 selectivity, these considerations will help veterinarians select and treat patients that could benefit from this new class of NSAID.