Muscle relaxant properties of the identified metabolites of dantrolene.

Identified metabolites of dantrolene, a skeletal muscle relaxant, were studied for inhibition of skeletal muscle contractions. Inhibition of muscle contractions were studied in vivo in the rat gastrocnemius muscle preparation, and in vitro using isolated rat diaphragm strips. Dantrolene (D) and 5-hydroxydantrolene (5-HD) inhibited muscle contraction responses in a dose dependent manner, both in vivo and in vitro. 5-HD was less potent than D.