Isoxsuprine

Isoxsuprine is a **peripheral vasodilator** primarily used in veterinary medicine for the management of **navicular disease** in horses, though its oral efficacy has been recently questioned due to poor bioavailability. * **Equine Use**: Historically prescribed to improve blood flow to the hoof and podotrochlea. Also used anecdotally as a tocolytic agent. * **Canine Use**: Anecdotally used for **Raynaud's-like syndrome** (periodic digital cyanosis, onychogryphosis). * **Avian Use**: May improve microcirculation. **Clinical Pearl**: Because of its significant first-pass metabolism, oral administration in horses often fails to achieve detectable plasma concentrations, leading many modern practitioners to question its clinical utility for navicular syndrome compared to other hemorrheologic agents like pentoxifylline.

กลไกการออกฤทธิ์: Isoxsuprine acts as a **beta-adrenergic agonist** (specifically **beta-2 receptors**), though its vasodilatory effects may also stem from direct smooth muscle relaxation independent of beta-receptors. * **Vasodilation**: Stimulates **beta-2 receptors** → increases intracellular **cAMP** → decreases intracellular calcium → **vascular smooth muscle relaxation** (primarily in skeletal muscle). * **Uterine Relaxation**: Relaxes uterine smooth muscle, acting as a tocolytic agent. * **Hemorrheologic Effects**: At high doses, it can decrease blood viscosity and reduce platelet aggregation. * **Cardiac Effects**: May exhibit positive inotropic and chronotropic effects on the heart via **beta-1 receptor** stimulation. * **Analgesia**: Does not appear to possess significant analgesic properties in horses.

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