Amrix had similar efficacy to cyclobenzaprine immediate-release (CIR) taken three times a day in alleviating acute muscle spasm associated with lower back and neck pain. In addition, less daytime drowsiness was observed with Amrix (cyclobenzaprine hydrochloride extended-release capsules) compared to CIR, although such a comparison was not pre-specified in the statistical analysis plan.
The data, which were the basis for the FDA approval of Amrix, were pooled from two identical 14-day multicenter studies, evaluating a total of 504 adults across four study arms (Amrix 15mg, Amrix 30mg, placebo, and CIR 10mg three times daily). These participants had moderate-to-severe muscle spasm of cervical or lumbar origin associated with local pain, tenderness, limitation of motion, and restrictions of daily living.