Editor's comment: Mirtazapine (brand name Remeron) is a tetracyclic antidepressant. It is not known exactly how mirtazapine works but it is thought to increase the activity of certain chemicals in the brain (eg, norepinephrine, serotonin).
Efficacy and Safety of Mirtazapine in Fibromyalgia Syndrome Patients: A Randomized Placebo-Controlled Pilot Study (July/August).
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.
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.
Source: The Annals of Pharmacotherapy, June 4, 2013. By Suwimon Yeephu, Chuthamanee Suthisisang, Saithip Suttiruksa, Pradit Prateepavanich, Patchara Limampai, and Irwin Jon Russell. Department of Pharmacology, Mahidol University, Rajthevee, Bangkok, Thailand.