Dantrolene--a review of its pharmacology, therapeutic use and new developments.

Human malignant hyperthermia is a life-threatening genetic sensitivity of skeletal muscles to volatile anaesthetics and depolarizing neuromuscular blocking drugs occurring during or after anaesthesia. The skeletal muscle relaxant dantrolene is the only currently available drug for specific and effective therapy of this syndrome in man. After its introduction, the mortality of malignant hyperthermia decreased from 80% in the 1960s to < 10% today. It was soon discovered that dantrolene depresses the intrinsic mechanisms of excitation-contraction coupling in skeletal muscle. However, its precise mechanism of action and its molecular targets are still incompletely known. Recent studies have identified the ryanodine receptor as a dantrolene-binding site. A direct or indirect inhibition of the ryanodine receptor, the major calcium release channel of the skeletal muscle sarcoplasmic reticulum, is thought to be fundamental in the molecular action of dantrolene in decreasing intracellular calcium concentration. Dantrolene is not only used for the treatment of malignant hyperthermia, but also in the management of neuroleptic malignant syndrome, spasticity and Ecstasy intoxication. The main disadvantage of dantrolene is its poor water solubility, and hence difficulties are experienced in rapidly preparing intravenous solutions in emergency situations. Due to economic considerations, no other similar drugs have been introduced into routine clinical practice.