Man with back pain sitting on bench at the outdoor. People, health care and medicine concept

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KENSINGTON, Australia — Muscle relaxers, one of the most common medications prescribed for backaches, are largely ineffective, according to a new study. They might even increase the risk of side effects such as headaches and dizziness, say scientists.

An analysis of the latest evidence shows that muscle relaxants might reduce pain in the short term, but the effect is “too small” to be considered clinically meaningful. However, the researchers stress that the certainty of evidence is low and say large trials are urgently needed to resolve uncertainties around the use of muscle relaxers for back pain.

Lower back pain is a major health problem around the world and muscle relaxers — a broad class of drugs that include non-benzodiazepine antispasmodics and antispastics — are a frequently prescribed treatment. In 2020, prescriptions in the U.S. exceeded 30 million. However, around the world, clinical practice guidelines provide conflicting recommendations for their use. 

Researchers in Australia investigated the effectiveness, acceptability, and safety of muscle relaxers compared with a placebo, usual care, or no treatment in adults with non-specific lower back pain. They analyzed evidence from 31 trials involving more than 6,500 participants.

The trials were of varying quality, but the researchers were able to assess the certainty of evidence using the recognized Grading of Recommendations, Assessment, Development and Evaluations (GRADE) system. They set a difference of at least ten points on a zero to 100 scale for pain and disability to be the smallest clinically important effect, a threshold used in other low back pain studies.

“Very low certainty evidence showed that non-benzodiazepine antispasmodic drugs might reduce pain intensity at two weeks or less for patients with acute lower back pain compared with controls. But this effect is small — less than eight points on a zero to 100-point scale — and does not meet common thresholds to be clinically meaningful,” according to a BMJ media release. “There was little to no effect of non-benzodiazepine antispasmodics on pain intensity at three to 13 weeks or on disability at all follow-up time points. Low and very low certainty evidence also showed that non-benzodiazepine antispasmodics might increase the risk of adverse events — commonly dizziness, drowsiness, headache, and nausea — and might have little to no effect on treatment discontinuation compared with controls. No trials evaluated the effect of muscle relaxants on long term outcomes.”

Although the analysis was based on the best available trial evidence, the researchers acknowledge some limitations and say the modest overall effect could still mean that some, but not all, patients gain a worthwhile benefit. However, they stress that the low-to-very low certainty of evidence does not allow any firm recommendations.

“We would encourage clinicians to discuss this uncertainty in the efficacy and safety of muscle relaxers with patients, sharing information about the possibility for a worthwhile benefit in pain reduction but increased risk of experiencing a non-serious adverse event, to allow them to make informed treatment decisions,” the authors write. “Large, high quality, placebo-controlled trials are urgently needed to resolve uncertainties about the efficacy and safety of muscle relaxants for low back pain.”

The study is published in the peer-reviewed medical trade journal The BMJ.

SWNS writer Stephen Beech contributed to this report.

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