Skeletal muscle relaxant for the treatment of fibromyalgia: a systematic review and meta-analysis of randomized controlled trials

Background/importance: Fibromyalgia is a complex chronic pain disorder that significantly impairs patient well-being. Evaluating the efficacy of muscle relaxants for treating fibromyalgia is crucial for improving patient care.

Objective: This study aimed to evaluate the analgesic efficacy of muscle relaxants in patients with fibromyalgia.

Evidence review: A comprehensive literature search was conducted using PubMed, EMBASE, Web of Science, ClinicalTrials.gov, and the Cochrane Library. The search included randomized controlled trials (RCTs) comparing skeletal muscle relaxants with placebo/active analgesics for fibromyalgia. The primary outcome was pain intensity, measured by standardized mean difference (SMD) in pain scores. The risk of bias of included RCTs was assessed using the Cochrane Risk of Bias Assessment Instrument for Randomized Controlled Trials.

Findings: 14 RCTs (1851 participants) were included. Muscle relaxants were associated with a small but statistically significant reduction in pain scores compared with placebo or active treatment (SMD=-0.24, 95% CI=-0.32 to -0.15, p<0.001, 95% prediction interval=-0.40 to -0.08), with no significant inconsistency (I²=0, 95% CI=0% to 50.79%) and a moderate Grading of Recommendation, Assessment, Development and Evaluation rating. Secondary outcomes showed small, but statistically significant improvements in depression, fatigue and sleep quality. Muscle relaxants were associated with increased incidence of overall adverse effects, fatigue, abnormal taste, and drug withdrawal due to adverse effects.

Conclusions: Moderate quality evidence showed that muscle relaxants were associated with a small reduction in pain intensity for patients with fibromyalgia.