For use as a vasodilator, Isoxsuprine hydrochloride is given orally in doses of 10 to 20 mg 3 or 4 times daily. To arrest premature labor, Isoxsuprine hydrochloride is given initially by intravenous infusion in doses of 200 to 500 mcg/minute, adjusted according to the patient's response, until control is achieved. Once labor has been arrested intramuscular injections of 10 mg are given every 3 to 8 hours. Prophylaxis may be continued orally with 30 to 90 mg daily.