Efficacy and tolerability of cyclobenzaprine extended release for acute muscle spasm: a pooled analysis

To assess the efficacy and tolerability of once-daily cyclobenzaprine extended release (CER) 15 and 30 mg in relieving acute muscle spasm.

This is a pooled analysis of 2 randomized, double-blind, placebo-controlled, parallel-group studies of identical design. Adults with local muscle spasm associated with neck/low back pain were randomized to treatment with once-daily CER 15 (n = 127) or 30 mg (n = 126), cyclobenzaprine immediate release (CIR) 10 mg 3 times daily (n = 123), or placebo (n = 128) for 14 days. Primary outcome measures were the patient's rating of medication helpfulness and physician's clinical global assessment of response to therapy at day 4.

Of 504 patients, 330 (65.5%) completed the studies. Significantly greater improvements in patient's rating of medication helpfulness were reported with CER 15 and 30 mg versus placebo at day 4 (P < 0.025). No differences were reported between groups in physician's clinical global assessment. Significantly greater improvements (P < 0.025) were noted in patient-rated secondary measures versus placebo: relief from local pain at days 4 (CER 30 mg) and 8 (CER 15 and 30 mg), global impression of change at days 4 and 8 (CER 30 mg), and restriction of movement at day 4 (CER 30 mg). Improvements with CER 15 and 30 mg on most efficacy measures were similar to CIR. There was less reported daytime drowsiness with CER 15 and 30 mg than with CIR (P < 0.05). Most adverse events (AEs) were mild in intensity. The most common AEs for all groups were dry mouth, constipation, dizziness, headache, and somnolence. The rate of somnolence reported as an AE was lower (P < 0.05) with CER 15 (0.8%) and 30 mg (1.6%) than with CIR (7.3%).

Once-daily CER was effective in relieving acute muscle spasm based on patient's rating of medication helpfulness at day 4 and was generally well tolerated with a low rate of reported somnolence.