Mirtazapine is commonly used to treat major depressive disorder. Due to its effects on multiple neurotransmitters, it has been investigated for possible benefits in patients with fibromyalgia. The objective of this systematic review is to assess the efficacy and safety of mirtazapine in the treatment of patients with fibromyalgia. Pubmed (1946-May 2018), Embase (1947-May 2018), CENTRAL, and ClinicalTrials.gov were queried using the search term combination: fibromyalgia, pain, chronic pain, neuralgia, neuropathic pain, chronic widespread pain, or chronic pain syndrome and mirtazapine. Studies appropriate to the objective were evaluated, including three randomized, placebo-controlled trials and one open-label trial, investigating the effect of mirtazapine in patients with fibromyalgia. In patients with fibromyalgia, treatment with mirtazapine resulted in improvements in pain, sleep, and quality of life. Study durations ranged from 6 to 13 weeks and studies used varying dosing strategies for mirtazapine. Minor occurrences of somnolence, weight gain, nasopharyngitis, dry mouth, and increased appetite were reported with mirtazapine use. Based on the reviewed literature, mirtazapine appears to be a promising therapy to improve pain, sleep, and quality of life in patients with fibromyalgia. These benefits were demonstrated in patients that were treatment naïve and those that had failed previous therapies. Additional clinical evidence through larger and longer length trials would be of benefit to further define the role of mirtazapine for patients with fibromyalgia.
Keywords: Chronic pain; Depression; Fatigue; Pain; Quality of life; Sleep.