The effect of dantrolene sodium in relation to blood levels in spastic patients after prolonged administration.

In 25 patients with spasticity, pharmacokinetics and effects of dantrolene sodium were investigated after prolonged administration. A beneficial effect occurred in seven patients. The results were better on 100 mg daily than on a higher daily dose. An increase of the daily dose from 200 to 400 mg was not associated with higher blood levels. Many side effects were noted such as: anorexia, nausea, drowsiness, depression and muscle weakness. From this study we conclude that dantrolene sodium is a muscle relaxant with a weak to moderate effect in patients with spasticity; the effect at doses higher than 200 mg daily is probably poor.