Simultaneous determination of dantrolene and its metabolites, 5-hydroxydantrolene and nitro-reduced acetylated dantrolene (F 490), in plasma and urine of man and dog by high-performance liquid chromatography.

A reversed-phase high-performance liquid chromatographic method is described for the simultaneous determination of the skeletal muscle relaxant dantrolene and its metabolites, 5-hydroxydantrolene and nitro-reduced acetylated dantrolene (F-490), in plasma and urine of man and dog. The substances are detected spectrophotometrically at 375 nm. The detection limits are 0.02 mg/l. A preliminary extraction step into a choloroform-butanol mixture is required for the plasma samples. The method is suitable for pharmacokinetic studies of dantrolene.