Dantrolene is a lipophilic hydantoin derivative that easily crosses cell membranes and achieves wide tissue distribution. It is unique among antispasticity drugs in that it works at the level of the skeletal muscle. Normally, muscle membrane depolarization causes the release of calcium from the sarcoplasmic reticulum with a resultant contraction.
Dantrolene decreases calcium release. As a result, there is uncoupling of the contractile process and a reduction in the force of contraction. The percentage reduction of force for twitch or low frequency stimulation of muscle is much greater than for high frequency or tetanic stimulation because more calcium is released in the latter.
For unknown reasons, dantrolene has little effect on cardiac and smooth muscle fibers.
Gracies JM, Nance P, Elovic E, et al. Traditional pharmacological treatments for spasticity part II: general and regional treatments. Muscle Nerve 1997;20(suppl 6):S92-120.
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