title: Efficacy and safety of mirtazapine in fibromyalgia syndrome patients: a randomized placebo-controlled pilot study.
abstract: BACKGROUND
  Data from an open-label trial suggest that mirtazapine might prove useful in treatment of fibromyalgia syndrome (FMS).
  
  
  OBJECTIVE
  To obtain preliminary efficacy data of mirtazapine for estimation of sample size requirements for a Phase 2 clinical trial in FMS.
  
  
  METHODS
  This 13-week randomized controlled trial compared the effects of mirtazapine 15 mg/day, mirtazapine 30 mg/day, and placebo in 40 patients with FMS. The primary outcomes were change in Pain Visual Analog Scale (PVAS) and proportion of pain responders (≥30% PVAS reduction). Secondary outcomes included scores from the Jenkins Sleep Scale (JSS), Patient Global Impression of Change (PGIC), Fibromyalgia Impact Questionnaire (FIQ), Hamilton Depression Rating Scale (HAM-D), Patient Global Assessment, and self-reported adverse events.
  
  
  RESULTS
  Significant within-group PVAS reductions from baseline were observed in all 3 groups, with the greatest improvement in the mirtazapine 30-mg group (p < 0.005); between-group difference was not significant. The proportion of pain responders did not meet significance criteria (66.67% for mirtazapine 30 mg, 50% for mirtazapine 15 mg, 41.67% for placebo). Significant within-group improvement in JSS scores was seen for mirtazapine 30 mg (p < 0.01) and mirtazapine 15 mg (p < 0.05). Between-group comparison achieved significance for JSS item 3, waking several times per night (p < 0.05). On the PGIC, 72.73% felt better with both mirtazapine dosages compared with 50% for placebo. Within-group FIQ responses indicated improvement in only mirtazapine-treated groups, whereas within-group improvement for HAM-D and Patient Global Assessment was observed in all groups. Based on our findings, the sample size requirement (80% power, 5% type I error) should be 83 per group to detect PVAS change difference between mirtazapine 30 mg and placebo. Common mirtazapine-related adverse events were increased appetite and weight gain.
  
  
  CONCLUSIONS
  Patients with FMS taking mirtazapine exhibited within-group significant improvement in most of the measured outcomes. Between-group analysis was predictably compromised by the small sample size. Mirtazapine was well tolerated. Further study with a larger sample size is likely to be useful.
authors.affiliation: Faculty of Pharmacy, Department of Pharmacology, Mahidol University, Rajthevee, Bangkok, Thailand.
authors.forename: Suwimon
authors.initials: S
authors.lastname: Yeephu
authors.forename: Chuthamanee
authors.initials: C
authors.lastname: Suthisisang
authors.forename: Saithip
authors.initials: S
authors.lastname: Suttiruksa
authors.forename: Pradit
authors.initials: P
authors.lastname: Prateepavanich
authors.forename: Patchara
authors.initials: P
authors.lastname: Limampai
authors.forename: Irwin Jon
authors.initials: IJ
authors.lastname: Russell
mesh_terms: D000328:Adult; D004244:Dizziness / Q000139:chemically induced / Q000175:diagnosis; D004311:Double-Blind Method; D005221:Fatigue / Q000139:chemically induced / Q000175:diagnosis; D005260:Female; D005356:Fibromyalgia / Q000175:diagnosis* / Q000188:drug therapy* / Q000523:psychology; D006801:Humans; D008803:Mianserin / Q000009:adverse effects / Q000031:analogs & derivatives* / Q000627:therapeutic use; D008875:Middle Aged; D000078785:Mirtazapine; D010147:Pain Measurement / Q000187:drug effects* / Q000379:methods; D010865:Pilot Projects; D011446:Prospective Studies; D013577:Syndrome; D016896:Treatment Outcome
chemical_list: D008803:Mianserin; D000078785:Mirtazapine