A SURVEY OF THE EFFECTS OF ISOXSUPRINE ON NONVASCULAR SMOOTH MUSCLE

¹ Department of Pharmacology, Research Division, Mead Johnson & Company, Evansville, Indiana

Isoxsuprine, an agent of known vasodilator effectiveness, was shown to be a potent inhibitor of various types of smooth muscle. In vitro, it was similar to papaverine in many respects. The most outstanding differences were its lesser ability to antagonize acetylcholine and to inhibit intestinal smooth muscle, and its greater potency in antagonizing l-norepinephrine and oxytocin. In vivo, isoxsuprine had a relatively long duration of action and inhibited every type of smooth muscle tested. Results suggested that isoxsuprine has the highest degree of inhibitory activity against uterine and biliary muscle, and that it has the lowest activity against intestinal smooth muscle. Intermediate activity was observed on respiratory and ureteral smooth muscle. Concepts suggestive of the mechanism of action are discussed.