Clodronate improves lameness in horses without changing bone turnover markers.

BACKGROUND: Clodronate is prescribed to performance horses with lameness. Despite its clinical popularity, little research has been done to understand the effects of clodronate in the horse.

OBJECTIVES: Our objective was to determine if a single treatment with clodronate at the clinically approved dose altered bone remodeling, bone cell recruitment or lameness in the horse.

STUDY DESIGN: Twelve university-owned equestrian team competition horses with a history of forelimb lameness due to navicular syndrome were randomised to receive either 1.4 mg/kg clodronate (CLOD n = 6) or an equivalent volume of LRS (CONT; n = 6) in a blinded manner.

METHODS: Blood was evaluated weekly for 8 weeks before and after drug administration (clodronate or placebo) for bone turnover markers CTX-I and osteocalcin. Lameness evaluations were performed to assess for change in lameness one week before and one, 2, 3 and 8 weeks after drug administration. Coach questionnaires were performed to assess for change in ridden performance one, 2, 3 and 8 weeks after drug administration. Bone cell recruitment was evaluated in vitro 2 weeks before and after drug administration.

RESULTS: There were no differences in in vitro bone cell recruitment from whole bone marrow or in bone turnover markers CTX-I or osteocalcin. A small but significant decrease in forelimb lameness was detected in CLOD treated horses one week after treatment (p = 0.005). There were no significant differences in hindlimb lameness. Coaches identified an improvement in performance significantly more often in CLOD vs. CONT (p = 0.01) at week 8.

MAIN LIMITATIONS: Two CONT horses received intra-articular anti-inflammatory medication after treatment, which may have altered lameness results.

CONCLUSIONS: A single dose of clodronate appears to reduce lameness without producing detectable effects on bone turnover markers. Due to the long half-life of a bisphosphonate drug, the effect of multiple doses on bone remodeling and lameness should be investigated. This article is protected by copyright. All rights reserved.