Fibromyalgia, milnacipran and experimental pain modulation: study protocol for a double blind randomized controlled trial

BACKGROUND: The prevalence of fibromyalgia increases worldwide and is characterized by widespread and chronic pain. Treatment is difficult and includes both drug and non-drug approaches. Milnacipran, an antidepressant, is used for fibromyalgia, with a possible beneficial effect on central pain modulation. Our hypothesis is that the efficacy of milnacipran in fibromyalgia depends on the performance of pain inhibitory controls. METHODS/DESIGN: A randomized, double blind, clinical trial (NCT01747044) with two parallel groups, in 48 women with fibromyalgia, is planned in the Clinical Pharmacology Center, University Hospital, Clermont-Ferrand, France. Conditioned pain modulation (estimated with thermal stimuli using a numeric pain rating scale), the primary endpoint measure, is evaluated before and one month after treatment with milnacipran or placebo. Secondary outcome measures include the predictability of pain descending pathways performance for milnacipran efficacy, tolerance and cognitive function. Data analysis is performed using mixed models; the tests are two-sided, with a type I error set at alpha = 0.05. Not only will this trial allow estimation of the beneficial effect of milnacipran on pain and on descending pain pathways but it will also evaluate whether the performance of this modulatory system could be predictive of its efficacy in alleviating pain. DISCUSSION: This method would allow clinicians to take a pro-active attitude by performing a rapid psychophysical test before starting milnacipran treatment and would avoid unnecessary prescription while preventing therapeutic failure in patients who often face this recurrent problem. TRIAL REGISTRATION: ClinicalTrials.gov NCT01747044.