Dantrolene sodium (sold under a variety of trade names) is a postsynaptic muscle relaxant with multiple indications in the fields of anesthesiology and neurology. Among the many indications for the use of dantrolene, its primary indication, and FDA approved usage in both children and adults, is for the treatment of malignant hyperthermia: the very rare, but life-threatening disorder triggered by general anesthesia. Malignant hyperthermia is a reaction to the volatile halogenated anesthetics, or depolarizing muscle relaxants, causing sustained muscle contraction, hyperthermia, rhabdomyolysis, and hypercarbia; potentially leading to intraoperative patient demise. These symptoms develop as a response to the anesthetic agents acting on defective ryanodine receptors (calcium channels in muscle cell sarcoplasmic reticulum). Given the mechanism of action, dantrolene acts as an antagonist to these receptors, therefore halting and preventing the further progression of the symptoms of malignant hyperthermia. Even though the incidence of susceptibility to malignant hyperthermia is estimated to be 1:50,000-100,000,[1] it is required, according to the Malignant Hyperthermia Association of the United States, that any facility that administers malignant hyperthermia triggering agents (Isoflurane, desflurane, sevoflurane, and succinylcholine) should stock dantrolene in their facilities at all times. Other FDA approved uses for dantrolene include muscle spasticity disorders as seen with upper motor neuron disorders including stroke, spinal cord injury, cerebral palsy, and multiple sclerosis. It is the only FDA approved oral peripherally acting antispasmodic medication for these disorders.Dantrolene is also used for the treatment of neuroleptic malignant syndrome (given its similarity in presentation and symptoms to malignant hyperthermia) as well as for the overdose of 2,4-dinitrophenol (A banned "fat burner" medication that interrupts ATP synthesis and causes hyperthermia). However, these are considered off-label uses.Recently, dantrolene has been studied in the treatment of vasospasm following aneurysmal subarachnoid hemorrhage. Single dose administration of intravenous dantrolene was found to decrease arterial vasospasm although this remains an off-label use.[2] Interestingly, research on Alzheimer's disease has shown that increased intracellular calcium release modulates amyloid genetic processing in the brain, thereby promoting memory loss. Ryanodine receptors have been identified as a possible culprit of this phenomenon. Given this information, Dantrolene may serve as a potential future treatment for Alzheimer's disease, although further studies are required to test this hypothesis before it can be recommended for this use.[3]