Sildenafil, the active ingredient in Viagra, inhibits phosphodiesterase type 5 (PDE5) in horses, similar to its action in humans. This enzyme breakdown cGMP, a crucial molecule for smooth muscle relaxation. By blocking PDE5, sildenafil increases cGMP levels, leading to vasodilation and improved blood flow.
In horses, this mechanism primarily impacts the corpus cavernosum of the penis, facilitating penile erection. However, sildenafil also affects other vascular beds, potentially impacting blood pressure and pulmonary function. Dosage is critical; excessive amounts can cause hypotension.
Absorption and elimination vary depending on the administration route (oral, intravenous). Oral administration generally results in slower onset and longer duration of action compared to intravenous administration. Metabolic pathways are also similar to those in humans, primarily involving hepatic metabolism via cytochrome P450 enzymes.
Potential side effects include: hypotension, gastrointestinal upset, and altered vision. Always consult with a veterinarian before using sildenafil in horses, considering the horse’s overall health, other medications, and the specific clinical indication.
| PDE5 Inhibition | Increased cGMP, vasodilation |
| Primary Target | Penile Corpus Cavernosum |
| Pharmacokinetics | Variable based on administration route |
| Metabolism | Primarily hepatic |
| Side Effects | Hypotension, GI upset, visual changes |
Remember, off-label use of sildenafil in horses requires careful monitoring and veterinary oversight. Always prioritize the horse’s well-being and adhere to established veterinary practices.
