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Lower placebo responses after long-term exposure to fibromyalgia pain

Kosek, Eva, Rosen, Annelie, Carville, Serena, Choy, Ernest Ho Sing, Gracely, Richard H., Marcus, Hanke, Petzke, Frank, Ingvar, Martin and Jensen, Karin B. 2017. Lower placebo responses after long-term exposure to fibromyalgia pain. Journal of Pain 18 (7) , pp. 835-843. 10.1016/j.jpain.2017.02.434

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Knowledge about placebo mechanisms in patients with chronic pain is scarce. Fibromyalgia syndrome (FM) is associated with dysfunctions of central pain inhibition, and since placebo analgesia entails activation of endogenous pain inhibition, we hypothesized that long-term exposure to FM pain would negatively affect placebo responses. Here we examined the placebo-group (n=37, mean age 45 years) from a 12-week, randomized, double-blind, placebo-controlled trial investigating the effects of milnacipran or placebo. 22 patients were classified as placebo non-responders and 15 as responders, according to the Patient Global Impression of Change (PGIC) scale. Primary outcome was the change in pressure pain sensitivity from baseline to post-treatment. Secondary outcomes included ratings of clinical pain (VAS), FM impact (FIQ) and pain drawing. Among placebo responders, longer FM duration was associated with smaller reductions in pressure pain sensitivity (r=0.689, p=.004), but not among non-responders (r=-0.348, p=.112). Here, we demonstrate that FM duration influences endogenous pain regulation, as pain levels and placebo-induced analgesia were negatively affected. Our results point to the importance of early FM interventions, as endogenous pain regulation may still be harnessed at that early time. Also, placebo-controlled trials should take FM duration into consideration when interpreting results. Clinical trial registration EudraCT 2004-004249-16.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Medicine
Systems Immunity Research Institute (SIURI)
Uncontrolled Keywords: Placebo analgesia fibromyalgia long-term pain chronic pain pain inhibition
Publisher: Elsevier
ISSN: 1526-5900
Date of First Compliant Deposit: 20 March 2017
Date of Acceptance: 21 February 2017
Last Modified: 28 Apr 2018 12:47

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