Muscle Relaxants for Chronic Pain: Where Is the Evidence?

TOPLINE:

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.

METHODOLOGY:

• Researchers conducted a systematic review to evaluate the effectiveness of long-term use (≥ 4 weeks) of muscle relaxants for chronic pain lasting ≥ 3 months.
• They identified 30 randomized clinical trials involving 1314 patients and 14 cohort studies involving 1168 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.

TAKEAWAY:

• The 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.
• 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.
• 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. Other adverse events included vomiting, diarrhea, nausea, weakness, and constipation.

IN PRACTICE:

“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. This may be particularly true for older patients for whom risks of adverse events may be greater,” the authors wrote. “Clinicians should be vigilant for adverse effects and consider deprescribing if pain-related goals are not met,” they further added.

SOURCE:

This study, led by Benjamin J. Oldfield, MD, MHS, Yale School of Medicine, New Haven, Connecticut, was published online on September 19, 2024, in JAMA Network Open.

LIMITATIONS:

This 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. 

DISCLOSURES:

The study was supported by the National Institute on Drug Abuse. The authors declared no conflicts of interest.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.