To determine the efficacy and safety of muscle relaxants in pain management in patients with inflammatory arthritis (IA).
We searched the Cochrane Central Register of Controlled Trials, Medline, Embase, and PsychINFO for randomized controlled trials in adults with IA that compared any muscle relaxant (administered via any route) to another analgesic intervention or placebo. We also searched the 2008-2009 American College of Rheumatology and European League Against Rheumatism abstracts and performed a hand search of reference lists of relevant articles. Primary outcomes were patient-reported pain relief ≥ 30% and withdrawals due to adverse events. Two authors independently assessed methodological quality and extracted data.
Six trials (126 participants) were included in this review. All trials were deemed to have a high risk of bias. Five crossover trials evaluated benzodiazepine; 4 assessed diazepam (n = 71), and one assessed triazolam (n = 15). The sixth trial, a parallel-group study, evaluated zopiclone (non-benzodiazepine, n = 40). No trial was longer than 2 weeks and 3 single-dose trials assessed outcomes at 24 hours only. Overall, the included trials failed to find evidence of a beneficial effect of muscle relaxants over placebo (at 24 hours, 1 week, or 2 weeks) or in addition to nonsteroidal antiiflammatory drugs (at 24 hours) on pain intensity, function, or quality of life. Data from 2 trials of longer than 24-hour duration (diazepam and zopiclone, n = 74) found that participants who received a muscle relaxant had significantly more adverse events compared with those who received placebo [number needed to harm (NNTH) 3, 95% CI 2 to 7]. These were predominantly central nervous system side effects including dizziness and drowsiness (NNTH 3, 95% CI 2 to 11).
Based upon the currently available evidence in patients with IA, benzodiazepines (diazepam and triazolam) do not appear to be beneficial in improving pain over 24 hours or 1 week. The non-benzodiazepine agent zopiclone also did not significantly reduce pain over 2 weeks. However, even short-term muscle relaxant use (24 hours to 2 weeks) is associated with significant adverse events, predominantly drowsiness and dizziness.