Isoxsuprine is a beta-adrenergic agonist and a direct-acting peripheral vasodilator. It acts primarily on beta-2 adrenergic receptors in blood vessels, leading to smooth muscle relaxation and vasodilation. In the Indian clinical context, it is primarily used for the management of peripheral vascular diseases like Raynaud's phenomenon, arteriosclerosis obliterans, and Buerger's disease. It also has significant tocolytic properties and is used off-label to treat threatened preterm labor and dysmenorrhea.
Adult: Oral: 10-20 mg (2-4 ml of 5mg/ml solution) three or four times daily. Maximum: 80 mg/day.
Note: The oral solution (5mg/ml) should be measured with a calibrated dosing syringe or cup. Can be taken with or without food. If GI upset occurs, administer with meals. Do not mix with antacids.
Isoxsuprine exerts its effects primarily through beta-2 adrenergic receptor agonism, leading to activation of adenylate cyclase, increased intracellular cyclic AMP (cAMP), and subsequent relaxation of vascular and uterine smooth muscle. It also has mild alpha-adrenergic receptor blocking activity, which contributes to vasodilation. It may have a direct relaxant effect on smooth muscle independent of adrenergic receptors.
Pregnancy: Category C (US FDA). Animal studies show risk, human data limited. Used off-label as a tocolytic. Should only be used if potential benefit justifies potential risk to the fetus, under strict obstetric supervision.
Driving: May cause dizziness, lightheadedness, or syncope. Patients should not drive or operate machinery until their response is known.
| Other Vasodilators (e.g., Nitrates, Alpha-blockers) | Additive hypotensive effect; risk of severe hypotension. | Major |
| Beta-blockers (e.g., Propranolol) | Antagonizes the vasodilatory effect of Isoxsuprine. | Moderate |
| Sympathomimetics (e.g., Ephedrine, Pseudoephedrine) | Increased risk of tachycardia and hypertension. | Moderate |
| Antihypertensives | Enhanced blood pressure lowering effect. | Moderate |
| Oxytocic agents (e.g., Oxytocin, Methylergometrine) | Antagonizes the tocolytic effect of Isoxsuprine. | Major (in obstetric use) |