The FDA recently approved a new non-steroidal anti-inflammatory drug (NSAID) that can be applied to the skin over a horse’s joint to relieve pain of osteoarthritis. The approval represents the first topical equine pharmaceutical formulation of a compound called diclofenac that uses liposome technology–which allows medication to be absorbed straight to the site of the horse’s joint problem. This provides a new option for practitioners treating with NSAIDs, since a disadvantage of systemic NSAID use is that it has been shown to increase risk of gastrointestinal or renal toxicity.

The product, developed by IDEXX pharmaceuticals, is called SURPASS, and it will be available by veterinary prescription only.

Diclofenac has been used in humans for relief of pain and inflammation, and it has been available for oral, intravenous, intramuscular, intracolon, rectal, and topical administration. The drug is designed to inhibit cyclooxygenase activity and prostaglandin biosynthesis. Cyclooxygenase is an enzyme that directs production of prostaglandins, which are chemical substances that cause inflammation by increasing blood flow to the damaged tissue, make blood vessels more “leaky,” and produce pain in inflamed tissue. Therefore, the medication serves as a potent anti-inflammatory that acts as an analgesic (reduces pain) and antipyretic (reduces fever).

SURPASS is labeled for the treatment of equine osteoarthritis of the carpus (knee), tarsus (hock), fetlock, and pastern.

Joseph J. Bertone, DVM, MS, Dipl. ACVIM, now professor of equine medicine in the College of Veterinary Medicine at the Western University of Health Sciences, presented information on SURPASS field studies at the 2002 American Association of Equine Practitioners Convention in Orlando, Fla., while the drug was still under development. (Bertone was practicing with Alpine Animal Hospital in Carbondale, Colo., at the time of th