Does prior dantrolene affect the in vitro diagnosis of malignant hyperthermia susceptibility?

A therapeutic and prophylactic dose of dantrolene administered to malignant hyperthermia-susceptible pigs had no effect on the abnormal in vitro contracture response of subsequent muscle biopsies. The in vitro contracture response of MHS pig muscle to halothane and to caffeine was not altered by prior dantrolene treatment. It is concluded that prior dantrolene administration has no effect on the discrimination of porcine MSH by in vitro pharmacological testing.