Review of oral skeletal muscle relaxants for the craniomandibular disorder (CMD) practitioner

The presence of acute or chronic muscle pain and muscle spasm is a common finding in the treatment of craniomandibular disorders. A review of the literature on the centrally acting oral skeletal muscle relaxants is presented to assist the practitioner in treating CMD. The pharmacology, pharmacokinetics, metabolism, adverse reactions and available dosage forms of the skeletal muscle relaxants are discussed. The agents reviewed are carisoprodol, methocarbamol, chlorphenesin carbamate, metaxalone, chloroxazone, orphenadrine citrate, diazepam, and cyclobenzaprine. Their mechanisms are not well defined. Most act via selective inhibition of polysynaptic pathways in the central nervous system. Most evidence for their efficacy is based on subjective responses and there is question as to the adequacy of the clinical studies to date. Based on the data all of the relaxants (possibly excepting diazepam) are better than placebo based on subjective analyses. Although combinations with analgesics provide better symptom relief, no superiority over analgesics exists. No skeletal relaxant has been shown to be superior over any other oral relaxant. Based on recent clinical suspicions, further study of multiple pharmacologic effects of newer agents is indicated.