Long-term muscle relaxant benefits limited for certain conditions

The long-term use of skeletal muscle relaxants (SMRs) for chronic pain is beneficial only in patients with painful spasms or cramps and neck pain but not in those with low back pain, fibromyalgia, and headaches, according to the results of a systematic review and meta-analysis.

Researchers searched multiple online databases for randomized clinical trials (RCTs) and cohort studies with comparator groups wherein least 1-month duration of SMRs for chronic pain were assessed. The studies investigated a variety of chronic pain conditions, including low back pain, fibromyalgia, headaches, painful cramps or spasticity, and other syndromes. Risk of bias and quality were assessed.

A total of 30 RCTs involving 1,314 participants and 14 cohort studies with 1,168 participants met the eligibility criteria and were included in the meta-analysis. The studies were mostly short term, with the duration ranging from 4 to 6 weeks. Across the studies, nine unique SMRs were identified, including baclofen in 11 studies (25 percent), tizanidine in eight studies (18 percent), and cyclobenzaprine in seven studies (16 percent).

Pooled data showed that the strongest evidence for SMR effectiveness was for trigeminal neuralgia, neck pain, and painful cramps. On the other hand, SMR effectiveness for fibromyalgia, low back pain, and other syndromes was not superior to that of placebo.

Sedation and dry mouth were the most frequent adverse effects. RCTs had a low to moderate risk of bias, while the quality of cohort studies was fair to good.

The findings suggest that deprescribing of SMRs should be considered if pain-related goals are not met.