Time to Recovery in Patients with Acute Painful Musculoskeletal Conditions Treated with Extended-Release or Immediate-Release Cyclobenzaprine

Introduction: This post-hoc analysis examined time to recovery in patients with acute, painful musculoskeletal conditions following cyclobenzaprine extended release (CER; Amrix®, Cephalon, Inc., Frazer, PA, USA), cyclobenzaprine immediate release (CIR; Flexeril®, Pliva, Pomona, NY, USA), or placebo administration. Methods: Data were pooled from two identically designed, double-blind, placebo-controlled, parallelgroup studies. Adults with acute, painful local muscle spasm were randomized to once-daily CER 15 mg, once-daily CER 30 mg, three-timesdaily CIR 10 mg, or placebo for 14 days. Efficacy assessments were time to first rating of “a lot” or “complete” relief from local pain or restriction of movement and patient-rated medication helpfulness. Results: A total of 504 patients were randomized, and 330 (65.5%) completed the studies. Median times to “a lot” or “complete” relief from local pain were faster with CER 15 mg (6 days, P=0.016), CER 30 mg (5 days, P=0.002), and CIR (5 days, P=0.002) versus placebo (8 days). Time to “a lot” or “complete” relief from restriction of movement was faster with CER 30 mg (5 days, P=0.004) and CIR (5 days, P=0.009) versus placebo (7 days). Median times to “very good” or “excellent” medication helpfulness were 10 days (CER 15 mg, P=0.020), 8 days (CER 30 mg, P=0.004), and 7 days (CIR, P<0.001) versus >14 days (placebo). Dry mouth, constipation, dizziness, headache, and somnolence were the most commonly reported adverse events. Somnolence rates were lower with CER 15 mg (0.8%, P=0.008) and CER 30 mg (1.6%, P=0.028) versus CIR (7.3%). Conclusion: Relief from local pain and restriction of movement occurred sooner with CER and CIR than placebo. CER was associated with less somnolence than CIR.