Muscle Relaxants Ineffective for Low Back Pain and Fibromyalgia

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By Pat Anson

Muscle relaxants are increasingly prescribed “off label” as an alternative to opioid medication, but according to a new analysis they are no more effective than a placebo in treating fibromyalgia and low back pain. They may be beneficial, however, for patients suffering from muscle cramps, neck pain and trigeminal neuralgia.

Researchers reviewed 44 studies involving nearly 2,500 patients who were prescribed a muscle relaxant for various pain conditions. Nine skeletal muscle relaxants (SMRs) were assessed, drugs that were initially developed and then approved by the FDA as anti-spasticity and anti-spasmodic medications:

  • Carisoprodol (Soma)

  • Baclofen

  • Tizanidine

  • Cyclobenzaprine

  • Eperisone

  • Quinine

  • Orphenadrine

  • Chlormezanone

  • Methocarbamol

Despite a lack of evidence on their effectiveness beyond 3 weeks, prescribing of SMRs doubled between 2005 and 2016, with office visits for refills of SMR prescriptions tripling over the same period, indicating they were increasingly being used long-term and off-label. According to a 2021 study, over a third of patients prescribed SMRs did not have a musculoskeletal disorder, a sign of “unnecessary or inappropriate use.”

Researchers involved in the current study, published in JAMA Network Open, reached a similar conclusion that muscle relaxants are overprescribed.

“Despite increasing prevalence and increasing risks of their use, our systematic review suggests only limited evidence of efficacy for long-term use of SMRs for a small subset of pain syndromes,” wrote lead author Benjamin Oldfield, MD, an Assistant Clinical Professor of Internal Medicine at Yale School of Medicine.

“Evidence for effectiveness was strongest for SMRs used for muscle spasms, painful cramps, and neck pain; in studies of SMRs for fibromyalgia, low back pain, headaches, and other syndromes, some showed small benefits and some did not, and on balance studies did not suggest a benefit.”

Oldfield and his colleagues say physicians should consider deprescribing SMRs to pain patients who have been using them long-term without apparent benefit.   

Adverse side effects from SMRs include sedation, somnolence, dizziness and dry mouth. The FDA also warns against taking the drugs with opioids, which could raise the risk of respiratory depression and overdose.

SMRs also increase the risk of falls, fractures, and vehicle crashes. Because of those risks, muscle relaxants should be avoided altogether in elderly patients, according to the American Geriatrics Society.