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.
There was insufficient evidence to support the use of cyclobenzaprine in the treatment of MP. We identified only two small studies in which a total of 35 participants were given cyclobenzaprine, and it was not possible to estimate risks for benefits or harms. Further high quality RCTs of cyclobenzaprine for treating MP need to be conducted before firm conclusions on its effectiveness and safety can be made. Experts in this area should elect cut-off points for participants to identify whether a patient has achieved a clinically relevant reduction of pain (primary outcome), so that their results can be combined easily into future versions of this review.