Forty Days of Firocoxib Safe in Healthy Horses

Nonsteroidal anti-inflammatory drugs (NSAIDs), such as phenylbutazone or “bute,” have anti-inflammatory properties that help treat pain in horses, particularly chronic pain due to laminitis and osteoarthritis. Despite being routinely prescribed, NSAIDs are associated with side effects. One study showed prolonged use of an NSAID called firocoxib appeared safe in healthy horses, laying the groundwork for additional studies.^*

NSAIDs are commonly prescribed medications in both human and equine medicine and are generally considered safe. Nonetheless, this drug class is associated with some potentially serious side effects. Examples include gastrointestinal disease (gastric ulcers and colitis), liver toxicity, impaired blood flow to the kidneys, immune system suppression, and abortion. Studies show that horses treated with specific NSAIDs such as phenylbutazone, flunixin meglumine, or ketoprofen (i.e., the nonselective COX inhibitors) may have mild to severe anorexia, diarrhea, oral ulcers, and signs of colic within 12 days of treatment.

In contrast, firocoxib, considered a COX-2 inhibitor or a “second generation” NSAID, has a strong safety profile when used for up to 14 days.

“Many horses, such as those with osteoarthritis, require long-term or even lifelong NSAID therapy to maintain comfort, and the long-term safety of firocoxib remains unknown,” said Catherine Whitehouse, M.S., a Kentucky Equine Research nutritionist.

To determine the safety of long-term administration of firocoxib, seven healthy horses were given a 57-mg tablet (crushed and top-dressed on concentrate) once daily for 40 days. Blood samples were collected at baseline (day 0), and days 10, 20, 40, 55, and 70 of the study. Horses were also examined daily for clinical signs of abdominal pain, behavior, food and water intake, oral ulcers, fecal consistency, and body condition daily throughout the entire 70-day study period.

Significant differences in several of the blood parameters were noted throughout the study. Most notably, red blood cell counts, hemoglobin, white blood cells, total protein, two liver enzymes (AST and ALP), and creatinine were statistically different than baseline values after treatment with firocoxib began.

“Despite being significantly different, the values were considered by the researchers to not be associated with clinical adversity. Further, most of the values returned to pretreatment levels within 30 days after discontinuation of firocoxib,” Whitehouse said.

No horse included in the study showed any clinical signs of disease, including enterotoxicity (i.e., abdominal pain, oral ulcers, reduced food intake, or diarrhea) during the study.

Further studies using this NSAID for prolonged periods, as it would be used in a clinical setting, as well as in injured or diseased horses are needed.

“While NSAIDs play an important role in managing osteoarthritis-related discomfort, a multimodal treatment approach is recommended. This includes offering oral joint health supplements that contain glucosamine, chondroitin sulfate, and hyaluronic acid,” advised Whitehouse. “These joint health compounds work by maintaining joint function through several mechanisms targeting cartilage formation, reducing inflammation, and maintaining synovial fluid.”

Joint supplements can be added easily to a complete and balanced diet. Additionally, horses with osteoarthritis should maintain an ideal weight and body condition score.

“Overloaded joints due to excess body weight is detrimental and should be corrected as part of a robust joint health program,” Whitehouse recommended.

Check out Kentucky Equine Research’s body condition resources to develop an appropriate weight-management program.

^*Ignácio, F.S., L.V. Garcia, G.G. de Souza, L.Z. Amatti, L.D. de Barros, D.R. Bergfelt, G.S. Camargo, C. de Meria, and B.F.M. de Almeida. 2024. Hematological and biochemical effects associated with prolonged administration of the NSAID firocoxib in adult healthy horses. Veterinary Science 11(6):256.