IMPORTANCE: Stricter opioid prescribing guidelines have increased prescriptions of skeletal muscle relaxants (SMRs) for chronic pain, but the efficacy of long-term use of SMRs for chronic pain is unknown.
OBJECTIVE: To systematically review the effectiveness or efficacy of long-term use of SMRs for chronic pain.
EVIDENCE REVIEW: Two reviewers systematically searched Ovid MEDLINE, Embase (Ovid), Web of Science, CINAHL, and Cochrane through December 4, 2023. They included articles published in English, Spanish, or Italian. Only randomized clinical trials (RCTs) and cohort studies with comparator groups evaluating at least 1-month duration of SMRs for chronic pain were included. The reviewers dually reviewed data abstraction, risk-of-bias, and quality. They characterized studies by chronic pain syndrome: low back pain, fibromyalgia, headaches, painful cramps or spasticity, and other syndromes.
FINDINGS: A total of 30 RCTs with 1314 participants and 14 cohort studies with 1168 participants assessed SMRs for chronic pain. Studies were primarily short-term (4-6 weeks). Nine unique SMRs were represented by the studies identified. Eleven studies (25%) examined baclofen, 8 (18%) examined tizanidine, and 7 (16%) examined cyclobenzaprine. Evidence for effectiveness was strongest for SMRs used for trigeminal neuralgia, neck pain, and painful cramps; evidence suggested SMRs for fibromyalgia, low back pain, and other syndromes were not more beneficial than placebo. The most common adverse effects were sedation and dry mouth. RCTs had a low to moderate risk of bias, and the quality of cohort studies was fair to good.
CONCLUSIONS AND RELEVANCE: In this systematic review of long-term use of SMRs for chronic pain, findings suggest that their long-term use may benefit patients with painful spasms or cramps and neck pain; their long-term use for low back pain, fibromyalgia, and headaches did not appear to be beneficial. Clinicians should be vigilant for adverse effects and consider deprescribing if pain-related goals are not met.
| Discipline Area | Score |
|---|---|
| Family Medicine (FM)/General Practice (GP) |  |
| General Internal Medicine-Primary Care(US) | |
| Rheumatology | |
| Special Interest - Pain -- Physician |  |
Interesting article underlining a therapeutic use for a class of molecule that has generally been considered mostly harmful for chronic MSK pain.
Magical thinking.
I was disappointed after reading the paper. "Long-term use" in the title of the paper is misleading. In the literature, long-term studies are defined by a duration > 12 weeks, but the included studies were primarily short-term (4-6 weeks). The authors did not perform a quantitative synthesis of the data, but gave narrative descriptions of study results such as "demonstrated improvement." This leaves the the reader in the dark about the magnitude of the effects. They did not pool the dropout rates due to adverse events and serious adverse events, leaving the reader in the dark about the tolerability and safety.
