Spasmolytics, centrally acting

Dantrolene is a non-centrally acting spasmolytic that is used to treat and prevent malignant hyperthermia in pigs and humans. It limits the amount of calcium being released from the sarcoplasmic reticulum during malignant hyperthermia (Miller 1995). 

Both the beverage, kava or yangona, and the dried root of Piper methysticum are used as sources of a series of py-rones with biological activity. Kavalactones in this plant are diuretic, soporific, anticonvulsant, spasmolytic, local anesthetic, and antimycotic (Lebot, 1991). The dried root contains about 5-6% resin from which six related pyrones [yan-gonin (4), desmethoxyyangonin, kawain (5), dihydrokawain, methysticin (6), and dihydromethylsticin] have been isolated. All are more or less potent, centrally acting skeletal muscle relaxants that also possess antipyretic and local anesthetic properties (Tyler et al., 1981). 

Skeletal muscle relaxants fall into three major categories those that reduce spasticity, those that cause neuromuscular blockade and those that work at the cellular level. Spasmolytic agents (e.g. metho-carbamol, guaifenesin) act centrally whereas neuromuscular blockers (e.g. succinylcholine (suxamethonium), pancuronium, atracurium) act at the neuromuscular end plate to produce muscular relaxation. Dantrolene falls into the third category and acts within the muscle cell itself to produce relaxation. 

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