Use of zoledronate for treatment of a bone fragility disorder in horses

To assess clinical outcomes and scintigraphic findings in horses with a bone fragility disorder (BFD) treated with zoledronate (a nitrogen-containing bisphosphonate).

Prospective uncontrolled clinical trial.

10 horses with evidence of a BFD.

Signalment, history, and geographic location of horses' home environments were recorded. Physical examinations, lameness evaluations, and nuclear scintigraphy were performed. Diagnosis of a BFD was made on the basis of results of clinical and scintigraphic examination. Each horse was treated with zoledronate (0.075 mg/kg [0.034 mg/lb, IV, once]) at the time of diagnosis. Horses were reevaluated 6 months after treatment.

Affected horses were from the central and coastal regions of California and had ≥ 1 clinical sign of the disorder; these included scapular deformation (n = 2), lordosis (1), nonspecific signs of musculoskeletal pain (1), and lameness that could not be localized to a specific anatomic region (9). All horses had multiple sites of increased radiopharmaceutica uptake during initial scintigraphic evaluation of the axial skeleton and bones of 1 or both forelimbs. Six months after treatment, clinical improvement (defined as improvement in the lameness score, resolution of signs of musculoskeletal pain, or both) was detected in 9 of 10 horses; scintigraphic uptake was unchanged (n = 2) or subjectively decreased (8). No adverse effects attributed to zoledronate treatment were detected.

Treatment with zoledronate appeared to be useful in improving clinical outcome and scintigraphic findings in horses with a BFD; however, future placebo-controlled studies are necessary to accurately determine efficacy and long-term safety.