Cyclobenzaprine hydrochloride effect on skeletal muscle spasm in the lumbar region and neck: two double-blind controlled clinical and laboratory studies.

A new drug, Cyclobenzaprine hydrochloride (Flexeril), was compared with diazepam (Valium) and placebo in double-blind trials for efficacy in treating spasms and pain in the neck and low back. Complex recording methods involving clinical evaluations (graded), patient self-ratings, goniometry, motion analysis by computer, electromyography of controlled motions and detailed statistical analysis were used. Clinical improvement over two weeks was statistically significant in all treatment groups with a statistically significant preference for Cyclobenzaprine hydrochloride. The most striking improvements recorded were in the electromyographic findings, which showed statistically significant changes for the Cyclobenzaprine group. Clinical muscle spasms are not accompanied by increased myoelectric activity; the reverse is true. With improvement, myoelectric activity in back muscles is augmented during prescribed stressful movements as measured by electromyography and computer analysis combined with complex electrogoniometry.