Chlormezanone in primary fibromyalgia syndrome: a double blind placebo controlled study.

Primary fibromyalgia syndrome (PFS) is a common condition that often proves resistant to health interventions. Chlormezanone combines corrective effects on disturbed sleep with muscle-relaxant properties, and therefore could be of potential benefit in PFS. Forty-two female patients with PFS (mean age 49, range 24-72 years) were randomly and blindly allocated either chlormezanone 400 mg nocte or placebo. Patients were assessed by single observer at 0, 3 and 6 weeks of treatment; assessments included sleep quality, inactivity and morning stiffness, morning alertness, tender point score, mood change and global opinion (patient and observer). No beneficial therapeutic effect could be attributed to chlormezanone. Although there are problems in assessing severity of a predominantly subjective condition, this essentially negative finding is of interest in respect to the pathogenesis of PFS.