Duration of Flexeril (Cyclobenzaprine) Effectiveness for Back Spasms

Evidence-Based Timeframe for Effectiveness

• Peak effectiveness of cyclobenzaprine is demonstrated at 2-4 days, with skeletal muscle relaxants showing moderate superiority to placebo for short-term pain relief, according to the American College of Physicians, as published in the Annals of Internal Medicine 1, 2
• Clinical trials consistently evaluated treatment durations of 2 weeks or less, with the exception of a single 3-week trial, as reported in the Annals of Internal Medicine 1, 2, 3

Chronic Pain Context

• The American Society of Anesthesiologists guidelines note that literature is insufficient to evaluate efficacy of skeletal muscle relaxants, including cyclobenzaprine, in providing pain relief for patients with chronic pain, with a Category D evidence rating 4, 5
• There is insufficient evidence to support skeletal muscle relaxants for chronic pain, according to the American Society of Anesthesiologists guidelines, with only one lower-quality trial evaluating cyclobenzaprine for chronic low back pain 4, 5