ISOXSUPRINE HCL

Chemistry - A peripheral vasodilating agent, isoxsuprine occurs as an odorless, bitter-tasting, white, crystalline powder with a melting point of about 200°C. It is slightly soluble in water and sparingly soluble in alcohol.

Storage, Stability, Compatibility

Tablets should be stored in tight containers at room temperature (15-30°C).

Pharmacology - ISOXSUPRINE HCL

Isoxsuprine causes direct vascular smooth muscle relaxation primarily in skeletalmuscle. While it stimulates beta-adrenergic receptors it is believed that this action is not required forvasodilitation to occur. In horses with navicular disease, it has been demonstrated that isoxsuprinewill raise distal limb temperatures significantly. Isoxsuprine will also relax uterine smooth muscleand may have positive inotropic and chronotropic effects on the heart. At high doses, isoxsuprinecan decrease blood viscosity and reduce platelet aggregation.

Uses, Indications

Isoxsuprine is used in veterinary medicine principally for the treatment of navicular disease in horses. It has been used in humans for the treatment of cerebral vascular insufficiency, dysmenorrhea, and premature labor, but efficacies are unproven for these indications.

Pharmacokinetics - ISOXSUPRINE HCL

In humans, isoxsuprine is almost completely absorbed from the GI tract, butin one study that looked at the cardiovascular and pharmacokinetic effects of isoxsuprine in horses(Mathews and et 1986), bioavailability was low after oral administration, probably due to a highfirst-pass effect. After oral dosing of 0.6 mg/kg, the drug was non-detectable in the plasma and nocardiac changes were detected. This study did not evaluate cardiovascular effects in horses withnavicular disease, nor did it attempt to measure changes in distal limb blood flow. After IVadministration in horses, the elimination half-life is between 2.5 - 3 hours.
Contraindications/Precautions - Isoxsuprine should not be administered to animals immediatelypost-partum or in the presence of arterial bleeding.

Adverse Effects, Warnings

After parenteral administration, horses may show symptoms of CNSstimulation (uneasiness, hyperexcitability, nose-rubbing) or sweating. Adverse effects are unlikelyafter oral administration, but hypotension, tachycardia, and GI effects are possible.
Overdosage - Serious toxicity is unlikely in horses after an inadvertent oral overdose, butsymptoms listed in the Adverse Effects section could be seen. Treat symptoms if necessary. CNShyperexcitability could be treated with diazepam, and hypotension with fluids.

Drug Interactions

No clinically significant drug interactions have been reported for this agent.