Background: Cyclobenzaprine is a TCA billed as a “muscle relaxant,” but has no effect on motor neurons nor skeletal muscle. Opioids work at the mu-receptor for pain, but have known side-effects and abuse risk. There is little support for using these agents in addition to NSAIDs for acute LBP (Ann Emerge Med 2003; 41:818 and CJEM 2010; 12:30).
Single ED; randomized n = 323 pts with acute non-traumatic, non-radicular LBP.
10-day courses of naproxen (500mg BID) + APAP (325 or 650mg q 8h) plus either placebo vs cyclobenzaprine (5 or 10mg q 8 h) vs oxycodone (5 or 10mg q 8 h).
After 1 week, all groups improved similarly as measured by standard questionnaire. 31% still reported significant pain.
Conclusion: Opioids and so-called muscle relaxants (at least cyclobenzaprine) add little to NSAID treatment. Don’t use them for acute LBP.
JAMA 2015 Oct 20; 314:1572.