Fibromyalgia and Mirtazapine

There’s a study from Thailand on fibromyalgia and mirtazapine. S. Yeephu and colleagues üpublished: “Efficacy and Safety of Mirtazapine in Fibromyalgia Syndrome Patients: A Randomized Placebo-Controlled Pilot Study (July/August)”. Link: http://www.ncbi.nlm.nih.gov/pubmed/23737510. They concluded: „ 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.”

Not my conclusion! My conclusion is different!

In “results” we find the important sentence: “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).” Pain response had been defined: “The primary outcomes were change in Pain Visual Analog Scale (PVAS) and proportion of pain responders (≥30% PVAS reduction).” A reduction of 30% is convenient for drug companies, but doesn’t mean much for patients. If you look at the big study of pregabalin you’ll find a definition of a pain reduction of 50%. Have a look at my problems with pregabalin in the treatment of fibromyalgia at: http://rheumatologe.blogspot.de/2012/06/fibromyalgia-and-pregabalin-some-ideas.html. So a pain reduction of 30% is a goal easily achieved, but the drug didn’t even meet the primary endpoint. An increase in scores from the Jenkins Sleep Scale (JSS) is to be expected. “Common mirtazapine-related adverse events were increased appetite and weight gain.”

My conclusion is: mirtazapine failed to achieve a meaningful reduction of pain. The drug is useful in treating depressive disorders, but shouldn’t be used in the treatment of fibromyalgia. The drug might lead to weight gain and so hampers effective exercise therapy as an important part of effective multimodal therapy strategies.