A systematic review of the efficacy of venlafaxine for the treatment of fibromyalgia

Abstract

What is known and objective Fibromyalgia is a painful disease affecting 1-2% of the United States population. Serotonin and norepinephrine reuptake inhibitors (SNRIs), such as duloxetine and milnacipran, are well studied and frequently used for treating this disorder. However, efficacy data are limited for the SNRI venlafaxine despite its use in nearly a quarter of patients with fibromyalgia. Accordingly, we systematically reviewed the efficacy of venlafaxine for treatment of fibromyalgia. Methods PubMed, Web of Science and the Cochrane Database were searched using the terms 'venlafaxine' and 'fibromyalgia'. Results were classified as primary studies or review articles based on abstract review. References of review articles were evaluated to ensure no primary studies evaluating venlafaxine were overlooked. All clinical studies that investigated venlafaxine for the treatment of fibromyalgia were included and graded on strength of evidence. Results and discussion Five studies met the inclusion criteria, including 4 open-label cohort studies and 1 randomized, controlled trial. Study durations ranged from 6 weeks to 6 months, and study sizes ranged from 11 to 102 participants. Four of the five published studies reported improvement in at least one outcome. Generally consistent improvements were observed in pain-related outcome measures, including the Fibromyalgia Impact Questionnaire (range, 26-29% reduction; n = 2 studies), Visual Analog Scale (range, 36-45% reduction; n = 2 studies), McGill Pain Questionnaire (48% reduction; n = 1 study) and Clinical Global Impression scale (51% had significant score change; n = 1 study). However, the few studies identified were limited by small sample size, inconsistent use of outcomes and methodological concerns. What is new and conclusion Studies assessing the efficacy of venlafaxine in the treatment of fibromyalgia to date have been limited by small sample size, inconsistent venlafaxine dosing, lack of placebo control and lack of blinding. In the context of these limitations, venlafaxine appears to be at least modestly effective in treating fibromyalgia. Larger randomized controlled trials are needed to further elucidate the full benefit of venlafaxine.