Inconsistent Benefit vs Harm of Skeletal Muscle Relaxants for Chronic Pain Syndromes

Are skeletal muscle relaxants, such as baclofen, tizanidine, and cyclobenzaprine, safe and effective for the long-term treatment of chronic pain in adults?

The review found that the long-term use of skeletal muscle relaxants is no better than placebo for low back pain, fibromyalgia, and headaches. Evidence is minimal for beneficial relief from trigeminal neuralgia, painful nocturnal cramps, and neck pain. Because of the common adverse effects of drowsiness and dizziness, clinicians should deprescribe these medications in patients whose pain-related goals are not being met. (Level of Evidence = 2a)

The investigators searched multiple databases, including Medline, EMBASE, Web of Science, and Cochrane, and other reviews and bibliographies for studies that evaluated the long-term use of skeletal muscle relaxants for chronic pain syndromes. Eligible studies included randomized controlled trials (RCTs) and observational studies on the use of skeletal muscle relaxants for at least 4 weeks in adults with painful syndromes lasting 3 months or longer. The authors included articles published in English, Spanish, and Italian. Two individuals independently screened studies for inclusion criteria and methodologic quality using standard scoring systems. Disagreements were resolved by consensus discussion with a third reviewer.

A total of 44 articles, including 30 RCTs (n = 1,314) and 14 cohort studies (n = 1,168), met eligibility criteria. The risk of bias of the individual studies was low to moderate. Nine skeletal muscle relaxants were evaluated; the most common were baclofen, tizanidine, and cyclobenzaprine. Skeletal muscle relaxants were no more effective than placebo for low back pain, fibromyalgia, and headaches. There was an association between skeletal muscle relaxant use and significant improvement in nocturnal leg cramps, trigeminal neuralgia, and chronic cervical pain. Common adverse effects, including drowsiness and dizziness, affected overall quality of life.

Study design: Systematic review

Funding source: Government

Setting: Various (meta-analysis)

Reference: Oldfield BJ, Gleeson B, Morford KL, et al. Long-term use of muscle relaxant medications for chronic pain: a systematic review. JAMA Netw Open. 2024;7(9):e2434835.