Authors: Friedman BW et al.
JAMA 2015 Oct 20.
Neither cyclobenzaprine nor opioids are helpful as adjuncts to naproxen therapy for low back pain.
Cyclobenzaprine (Flexeril) is a tricyclic antidepressant that is viewed as having “muscle relaxant” properties, even though it has no effect on motor neurons or skeletal muscle. Opioids act at the mu receptor to decrease pain but are associated with addiction and death from overdose. Evidence for benefit of adding these agents to nonsteroidal anti-inflammatory therapy for acute low back pain would be generously described as limited, at best (NEJM JW Gen Med Jul 15 2003 and Ann Emerg Med 2003; 41:818; NEJM JW Emerg Med Mar 2010 and CJEM 2010; 12:30).
Investigators at a single academic emergency department randomized 323 patients with acute nontraumatic, nonradicular low back pain to receive a 10-day course of naproxen (500 mg twice daily) plus one of three regimens: placebo, cyclobenzaprine (5 or 10 mg every 8 hours), or oxycodone (5 or 10 mg every 8 hours) and acetaminophen (325 or 650 mg every 8 hours). After 1 week, improvement in scores on the Roland-Morris Disability Questionnaire (the primary outcome) was similar in all three groups. However, 31% of all patients still reported significant pain.
Back pain is vexing for providers and patients alike. Opioids and so-called muscle relaxants appear to add little to nonsteroidal anti-inflammatory medications. Cyclobenzaprine has sedative and anticholinergic side effects, and prescribing opioids for a condition that evidence-based consensus guidelines warn against can lead to abuse and addiction.