A review of three commonly prescribed skeletal muscle relaxants.

Skeletal muscle relaxants (SMR) are commonly used drugs prescribed for the treatment of muscle spasm and discomfort. Although many have been in use for decades, physicians may be unaware of the accumulating evidence of their risks, benefits, safety and side effects. This review examines the efficacy, side effects, and safety of three commonly prescribed SMRs: metaxalone, cyclobenzaprine, and carisoprodol. All three appear to have equal efficacy, but their side effects vary considerably. Metaxalone has the fewest reports of side effects, and no reports of major safety issues. Cyclobenzaprine, closely related to the tricyclic antidepressants, causes the expected lethargy and anticholinergic side effects, and may have some toxicity in overdose and in combination with other substances. Carisoprodol raises the greatest concern. Reports in the literature suggest a significant potential for physical and psychological dependence perhaps suggesting a potential for misuse. It also has, perhaps, the greatest toxicity. A secondary goal of this review is to stimulate more discourse about these commonly used, but poorly understood compounds.