Effects of mirtazapine on quality of life of Thai patients with fibromyalgia syndrome: a double-blind, randomized, placebo-controlled trial

Background: Fibromyalgia syndrome (FMS) is a physical and mood disorder that affects quality of life (QoL). Mirtazapine, which improves monoaminergic neurotransmission, may benefit patients with FMS. Objectives: To compare the QoL between Thai patients with FMS and healthy Thais, and investigate the effects of mirtazapine in a pilot study. Methods: We compared the QoL between 76 Thai patients with FMS and 80 healthy Thai volunteers (HVs). A double-blind, randomized, placebo-controlled trial using 40 patients with FMS was conducted using a block design with parallel assignment. QoL data were obtained at week 0 (baseline), and repeatedly for 13 weeks after receiving placebo or mirtazapine 15 or 30 mg/day. Results: The mean baseline of SF-36 QoL was significantly lower in all domains in patients with FMS than in HVs (bodily pain 33 vs 87, general health 36 vs 84, mental health 63 vs 82, physical functioning 59 vs 96, role limitation because of emotional problems 41 vs 92, role limitation because of physical problems 30 vs 96, social functioning 53 vs 93, and vitality 48 vs 75 (scale 0-100, P < 0.01 all domains). Mirtazapine (15 and 30 mg/day) significantly reduced pain scores and improved all domains except social functioning, while placebo produced no change from baseline. Eight patients withdrew because of adverse events including somnolence and weight gain; no benefit, or lack of compliance. Conclusions: The QoL of patients with FMS is lower than for healthy Thais. Mirtazapine is effective for reducing pain and improving QoL in patients with FMS.