Dantrolene--a new therapeutic approach to the neuroleptic malignant syndrome.

The Neuroleptic Malignant Syndrome (NMS) is a rare but severe affection (spontaneous mortality 30 to 50 per cent), associating fever, hypertonia with myolysis, and respiratory impairment. Its mechanism remains debatable: The origin of the hypertonia might be central (as phenothiazines and butyrophenones induce a blockade of dopaminergic receptors in the hypothalamus) or it might be muscular (with an impairment of the sarcoplasmic reticulum uptake of calcium in a genetically abnormal muscle, as is proven in malignant hyperthermia). Whatever the actual mechanism, the oral or intravenous administration of sodium dantrolene, a peripheral muscle relaxant agent which does not affect the neuromuscular transmission but prevents the calcium-dependent contraction of actin and myosine, has proved to be effective in three recent cases of NMS.