Thursday, October 25, 2007

Findings predict a poorer response to opioid painkillers for fibromyalgia patients

ANN ARBOR, Mich., Sept. 27 -- The reason that opioids seem to fizzle for fibromyalgia may be because of reduced receptor activity in regions of the brain that process and dampen pain signals, researchers here found.

Reduced ยต-opioid receptor-binding potential in fibromyalgia patients was also significantly correlated with depression and emotional components of pain, reported Richard E. Harris, Ph.D., of the University of Michigan, and colleagues, in the Sept. 12 issue of the Journal of Neuroscience.

"Because these receptors are the target of opiate drugs," they wrote, "a profound reduction in the concentration or function of these receptors is consistent with a poor response of fibromyalgia patients to this class of analgesics, observed anecdotally in clinical settings."

Alterations in central opioid neurotransmission in specific brain regions "suggest that these mechanisms, possibly as a consequence of persistent pain, are involved in the clinical presentation and even the perpetuation of symptoms in this illness," they added.

Regardless of whether the mechanism is high endogenous opioids or downregulation of opioid receptors, the findings predict a poorer response to opioid painkillers for fibromyalgia patients, they concluded.