Low-dose naltrexone in the treatment of fibromyalgia: A systematic review and narrative synthesis.

METHOD: A systematic literature search was conducted using the key words 'naltrexone', 'fibromyalgia', 'fibrositis', 'chronic pain' and 'neurogenic inflammation'. RESULTS: Manual exclusion led to the identification of 21 papers, with only five prospective controlled trials of low sample size. DISCUSSION: Low-dose naltrexone may be an effective and safe pharmacotherapy for patients with fibromyalgia. Current evidence lacks power and multisite reproduction.