The long-term use of muscle relaxants may benefit patients with painful spasms or cramps and neck pain, according to a systematic review of clinical studies, but they do not appear to be beneficial for low back pain, fibromyalgia, or headaches and can have adverse effects such as sedation and dry mouth.
In a systematic review to evaluate the effectiveness of long-term use (≥ 4 weeks) of muscle relaxants for chronic pain lasting ≥ 3 months, researchers identified 30 randomised clinical trials involving 1 314 patients and 14 cohort studies, involving 1 168 patients, grouped according to the categories of low back pain, fibromyalgia, painful cramps or spasticity, headaches, and other syndromes.
Baclofen, tizanidine, cyclobenzaprine, eperisone, quinine, carisoprodol, orphenadrine, chlormezanone, and methocarbamol were the muscle relaxants assessed in comparison with placebo, other treatments, or untreated individuals.
Reduced
Medscape reports that long-term use of muscle relaxants reduced pain intensity in those with painful spasms or cramps and neck pain. Baclofen, orphenadrine, carisoprodol and methocarbamol improved cramp frequency, while the use of eperisone and chlormezanone improved neck pain and enhanced the quality of sleep, respectively, in those with neck osteoarthritis.
But while some studies suggested that muscle relaxants reduced pain intensity in those with back pain and fibromyalgia, between-group differences were not observed. The benefits seen with some medications diminished after their discontinuation, said the researchers.
Despite tizanidine improving pain severity in headaches, 25% participants dropped out owing to adverse effects. Although certain muscle relaxants demonstrated pain relief, others did not.
The most common adverse effects of muscle relaxants were somnolence and dry mouth, while others included vomiting, diarrhoea, nausea, weakness, and constipation.
“For patients already prescribed long-term SMRs (skeletal muscle relaxants), interventions are needed to assist clinicians to engage in shared decision-making with patients about deprescribing SMRs,” the authors wrote.
“This may be particularly true for older patients for whom risks of adverse events may be greater, and clinicians should be vigilant, regarding adverse effects, and consider deprescribing if pain-related goals are not met.”
The study was led by Benjamin Oldfield, MD, MHS, Yale School of Medicine, and published online in JAMA Network Open.
Limitations
The systematic review was limited to publications written in English, Spanish and Italian language, potentially excluding studies from other regions. Variations in clinical sites, definitions of pain syndromes, medications, and durations of therapy prevented the possibility of conducting meta-analyses.
Only quantitative studies were included, excluding valuable insights into patient experiences offered by qualitative studies.
Study details
Long-term use of muscle relaxant medications for chronic pain: a systematic review
Benjamin Oldfield, Brynna Gleeson, Kenneth Morford et al.
Key Points
Question
What are the effectiveness and safety of long-term use of muscle relaxant medications for the treatment of chronic pain?
Findings
In this systematic review of 44 studies including 2482 participants, nine unique muscle relaxant medications were assessed. Muscle relaxants may be more beneficial than placebo for treating trigeminal neuralgia, painful cramps, and neck pain, but for fibromyalgia, low back pain, and other syndromes, they did not appear to be beneficial.
Meaning
These findings suggest that long-term use of muscle relaxants may only be beneficial for certain syndromes; clinicians should consider deprescribing if pain-related goals are not met.
Abstract
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 up to December 4, 2023. They included articles published in English, Spanish, or Italian. Only randomised 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 characterised 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.
Medscape article – Muscle Relaxants for Chronic Pain: Where Is the Greatest Evidence? (Open access)
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