Evidences on muscular relaxants for outpatient use: A review of the literature

Objective: To evaluate the evidence on the efficacy and adverse effects of oral muscle relaxants available in Brazil for spasticity, musculoskeletal conditions, fibromyalgia and tension headache. Methods: A literature review assessment was carried out based on systematic reviews published in the Medline, Virtual Health Library (VHL), Cochrane Library and National Institute for Health and Care Excellence (NICE) up to December 2016, that evaluated the drugs considered to be muscle relaxants by Anatomical Therapeutic Chemical (ATC) and available in Brazil in oral form: cyclobenzaprine, tizanidine, carisoprodol, orphenadrine and baclofen. Results: Twenty studies were identified, 17 of which were systematic reviews and three meta-analyzes. Evidence on the efficacy of muscle relaxants consists mainly of studies with poor methodological design. Comparison studies have not shown that one skeletal muscle relaxant is superior to another. Cyclobenzaprine demonstrated efficacy in musculoskeletal conditions, such as myofascial mandibular pain, fibromyalgia and low back pain. In fibromyalgia, it has shown benefit in overall improvement and sleep. In the management of low back pain, cyclobenzaprine showed modest effect, more present in the first four days. Carisoprodol in low back pain does not appear to have difference for cyclobenzaprine but this drug may cause dependence. Baclofen and tizanidine appear to be efficacious compared to placebo and equivalent in patients with spasticity. Conclusions: Muscle relaxants in general compared to placebo or to each other showed little evidence with significant statistics. Therefore the drug selection should be based on the profile of adverse effects, patient preference, potential of abuse, potential of interaction with other drugs, cost and other characteristics of the drugs.