Dantrolene is the only currently accepted specific treatment for MH. In an episode of MH, muscle metabolism is dramatically increased secondary to an increase in calcium within the muscle. This causes muscles to contract, ATP hydrolysis, and heat production. Dantrolene directly interferes with muscle contraction; decreasing calcium in muscle cells.
Dantrolene does not block neuromuscular transmission nor interfere with reversal of muscle relaxants. Although it does not block neuromuscular transmission, the mechanical response to nerve stimulation will be depressed, with subsequent potentiation of the non-depolarizing neuromuscular blockade. When dantrolene is used with non-depolarizing muscle relaxants, care should be taken to ensure muscle strength has returned prior to extubation.
Dantrolene may cause significant muscle weakness in patients with pre-existing muscle disease and should be used with extreme caution in those patients. Sterile phlebitis may follow administration of dantrolene, and should be infused through the largest possible vein. The sterile phlebitis can be later treated with warm soaks and elevation. When used with calcium channel blockers (verapamil or diltiazem), dantrolene may produce life-threatening hyperkalemia and myocardial depression. Otherwise there does not appear to be significant negative interaction with other drugs.
Once a patient has been successfully treated for 48 hours with intravenous dantrolene may be stopped and the blood tested daily until the CK level is trending down.