The evaluation of isoxsuprine hydrochloride for the treatment of navicular disease: a double blind study.
Authors: Turner, Tucker
Journal: Equine veterinary journal
Summary
Turner and Tucker's 1989 double-blind trial investigated whether isoxsuprine hydrochloride could effectively treat navicular disease, a concern that remains relevant given the condition's chronic nature and the limited pharmacological options available to practitioners. Twenty-eight horses were randomly assigned to receive placebo or isoxsuprine at three ascending doses (0.6, 1.2, or 1.8 mg/kg bodyweight), with clinical lameness assessments conducted throughout the study period. The medicated groups (n=22) demonstrated statistically significant improvement in clinical scores compared with placebo controls (n=6; P<0.01), though notably, efficacy did not increase with higher doses—suggesting a therapeutic threshold rather than a dose-response relationship. Interestingly, radiographic severity of navicular changes failed to correlate with either lameness severity or treatment response, indicating that radiological appearance alone cannot predict clinical outcomes or prognosis. For practitioners, these findings suggest isoxsuprine may offer genuine clinical benefit in managing navicular cases, though the lack of dose-escalation benefit implies no advantage to exceeding standard dosing protocols, and the disconnect between imaging and clinical response reinforces the need for thorough functional assessment alongside radiographic evaluation.
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Practical Takeaways
- •Isoxsuprine hydrochloride is an effective medical treatment for navicular disease with clinically significant benefits—consider as part of multimodal management strategy
- •Lowest effective dose (0.6 mg/kg) appears sufficient; higher doses do not provide additional benefit, reducing treatment costs
- •Radiographic appearance of navicular changes does not predict clinical outcome or response to medical therapy; clinical assessment is the more reliable prognostic indicator
Key Findings
- •Isoxsuprine hydrochloride treatment (22 horses) showed significant improvement in clinical assessment scores compared to placebo control (6 horses) at P < 0.01
- •No dose-dependent response observed across three treatment doses (0.6, 1.2, and 1.8 mg/kg bodyweight)
- •No correlation found between radiological evidence of navicular disease extent and severity of lameness or treatment response