Effects of topical nitroglycerine patches and ointment on digital venous plasma nitric oxide concentrations and digital blood flow in healthy conscious horses.
Authors: Gilhooly Meaghan H, Eades Susan C, Stokes Ashley M, Moore Rustin M
Journal: Veterinary surgery : VS
Summary
# Editorial Summary: Nitroglycerine Patches and Digital Perfusion in Horses Nitroglycerine (NTG) has been proposed as a therapeutic tool for laminitis management, with the rationale that topical application could reduce digital vasomotor tone and enhance blood flow to the foot—a key objective in acute laminitis treatment. Gilhooly and colleagues conducted a controlled experimental study on eight healthy horses, surgically implanting ultrasonic Doppler probes around the medial palmar digital artery and digital vein catheters to directly measure arterial blood flow and venous nitric oxide concentrations following application of NTG patches, NTG ointment or control patches over the digital vessels at fetlock level. Neither treatment produced statistically or biologically significant changes in digital arterial blood flow or venous plasma nitric oxide concentrations compared to controls, although a pilot intra-arterial NTG infusion did increase both parameters, suggesting the topical route fails to achieve sufficient digital tissue penetration. Whilst these findings do not definitively rule out NTG efficacy in the compromised vascular environment of acute laminitis, the lack of measurable vascular response in healthy horses raises serious questions about whether topical NTG formulations can reliably improve digital perfusion when clinically indicated. Practitioners relying on topical NTG patches or ointments for laminitis management should be aware that evidence-based support for this approach remains limited, and further investigation in diseased models is essential before recommending this treatment to clients.
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Practical Takeaways
- •Do not rely on topical nitroglycerin patches or ointments as a standalone therapy to improve digital blood flow in laminitis cases, as they do not achieve therapeutic vascular effects
- •If nitric oxide therapy is to be pursued, alternative delivery methods beyond topical application should be investigated, as topical formulations do not achieve adequate local concentrations
- •Current evidence does not support the use of NTG patches for managing digital vasomotor dysfunction in equine laminitis
Key Findings
- •Topical nitroglycerin patches and ointment produced no significant changes in digital arterial blood flow in healthy horses
- •Digital venous plasma nitric oxide concentrations did not increase significantly with topical NTG application
- •Intra-arterial NTG infusion did increase blood flow and NO concentrations in pilot study, suggesting systemic delivery is required
- •Topical NTG is unlikely to be effective for improving digital circulation in laminitic horses