Treating Navicular Disease From Inside the Bone

Healthy bone undergoes constant metabolic change to prevent bone loss or abnormal remodeling (cell turnover) that can occur with loading. Horses with navicular disease can have abnormal remodeling and formation of osteolytic lesions (areas of broken-down bone) within the navicular bone. This might be due to an imbalance in bone metabolism, with increased bone resorption. Dominique Thibaud, DVM, of Ceva Santé Animale (CEVA), in Libourne, France, with colleagues in France, Italy, and Germany, set out to evaluate a drug to target abnormal bone metabolism. The drug, tiludronate, inhibits excessive bone resorption, allowing bone metabolism to become balanced once again. The study aimed to assess tiludronate's effectiveness against navicular disease. (The drug is not approved in the United States for use in horses, so any clinical use would be considered off-label).

Fifty horses with moderate to severe navicular disease were studied. Radiographs and videotaped lameness examinations were collected prior to treatment. Horses were randomly assigned to receive either 1 mg/kg tiludronate intravenously (IV) daily for 10 days; 0.5 mg/kg IV daily for five days, followed by five days of placebo; or 10 days of IV placebo. Lameness exams were performed (and videotaped) one, two, and six months after treatment. Radiographs were repeated six months after treatment, and independent examiners reviewed all radiographs and lameness exam tapes. Horses which didn't respond to tiludronate or the placebo by two months, based on clinical examination and owner evaluation, were removed from the study as treatment failures and treated as needed with tiludronate.

Horses responded best (based on improvement of lameness and ability to return to work) to the regimen of 1 mg/kg tiludronate IV daily for 10 days. More recent cases of navicular disease (less than six months duration, 33 horses, no treatment failures) responded better than chronic cases (17 horses, 11 treatment failures). Of recent-case horses, 67% showed a positive response to treatment, and 75% returned to normal activity by six months.

Interestingly, horses had no change in flexion/extension test response after treatment. However, Thibaud notes, "Flexion/ extension tests assess local pain of the coffin joint, which can be due to both soft tissue and bone lesions. Tiludronate acts specifically on osteolytic bone lesions." So, some pain can remain in the foot despite improvement in the navicular bone. Overall, the results support Thibaud's opinion, "Tiludronate helps in restoring a normal balance between resorption and formation of bone" in horses with navicular disease. However, drug therapy should be combined with corrective shoeing for best results.

Thibaud is currently studying bone pharmacology in horses and other species. The CEVA web site (www.ceva.com) has prepared a link to a separate web site devoted to tiludronate, or Tildren, for horses at www.tildren.com.

Denoix, J.M.; Thibaud, D.; Riccio, B. Equine Veterinary Journal, 35 (4), 407-413, 2003.

About the Author

Susan Piscopo, DVM, PhD

Susan Piscopo, DVM, PhD, is a free-lance writer in the biomedical sciences. She practiced veterinary medicine in North Carolina before accepting a fellowship to pursue a PhD in physiology at North Carolina State University. She lives in northern New Jersey with her husband and two sons.

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