Reversible effect of dantrolene sodium on twitch tension of rat skeletal muscle.

The effect of dantrolene sodium on twitch tension in skeletal muscle of the rat was studied in short- and long-term experiments. The twitch tension is reduced to 50% of the control values within 20 to 30 minutes of drug administration. The recovery phase is considerably slower than the effect observed on the addition of dantrolene sodium, having a half time of 10 hours. Twenty-four hours after the drug injection, the twitch tension in the treated muscles is indistinguishable from that in the controls. It is shown that the reduction in the magnitude of the twitch produced by dantrolene sodium is slowly and completely reversible.