Dantrolene sodium: effects on smooth muscle.

The effects of dantrolene sodium on smooth muscle were evaluated in vitro using the guinea pig ileum and the guinea pig vas deferens preparations. Dantrolene irreversibly decreased the strength of the responses of the ileum to acetylcholine, histamine, potassium chloride and electrical stimulation. Doubling the concentration of calcium in the bathing media reduced the effect of dantrolene on all agonists. Dantrolene irreversibly decreased the response of the vas deferens to epinephrine, norepinephrine, acetylcholine and electrical stimulation. Doubling the concentration of calcium in the bathing media reduced the effect of dantrolene on all agonists. Dantrolene seems to depress smooth muscle as it does skeletal muscle. The mechanism of action probably involves the reduction of calcium flux into the muscles.