Safety of Clodronate in Horses with Navicular

Lameness-related performance issues must be swiftly and effectively diagnosed, a feat often easier said than done. Once the source of the lameness is discovered, appropriate treatment plan be devised so the horse may continue competing in comfort.

“In horses diagnosed with navicular syndrome, some veterinarians recommend a bisphosphonate. Currently, two different bisphosphonates are approved in horses, clodronate and tiludronate,” shared Laura Petroski-Rose, B.V.M.S, a Kentucky Equine Research veterinarian.

While the manufacturers and veterinarians report improvement in lameness following treatment of navicular horses with bisphosphonates, these medications have drawbacks.

“In human medicine, where these medications have been used for much longer, many well-known adverse effects of bisphosphonates exist. Some of those include bone fragility that can result in atypical fractures and a type of bone destruction called osteonecrosis that frequently affects the jaw,” said Petroski-Rose.

Despite being readily available and relatively widely used, one group of veterinarians* recently acknowledged that the research community is still learning about bisphosphonate use in horses. To explore the potential benefits and dangers of clodronate, 12 horses with a history of lameness associated with navicular discomfort were administered either the labeled dose of clodronate (1.4 mg/kg clodronate intramuscularly, maximum of 900 mg per horse) or a placebo control.

After only a single injection of clodronate, the veterinarians found a decrease in forelimb lameness and improved performance in all treated horses compared to the control group.

“Further, no evidence of increased bone turnover assessed by measuring blood levels of collagen breakdown and activity of osteoclasts, which are cells that breakdown bone, were noted,” Petroski-Rose reported.

These positive results, however, were obtained after only a single injection in a small group of horses, so a larger study is warranted.

“Veterinarians suggest that these medications do more than help horses with navicular syndrome. Bisphosphonates may actually help horses with other bone and joint disorders like osteoarthritis due to potential ‘off-target mechanisms,’ such as anti-inflammatory and pain-relieving features,” Petroski-Rose added.

Kentucky Equine Research has formulated several products designed to support bone growth, health, and lameness. Contact a nutrition advisor at Kentucky Equine Research for a personal recommendation.

*Mitchell, A., G. Wright, S.N. Sampson, et al. Clodronate improves lameness in horses without changing bone turnover markers. Equine Veterinary Journal. In press.