Why Don't Painkillers Work For People With Fibromyalgia?

[Guest guest]

Why Don't Painkillers Work For People With Fibromyalgia?

DentalPlans.com - Dania,FL*

9/27/2007

http://www.dentalplans.com/articles/25605/

Science Daily — People who have the common chronic pain condition

fibromyalgia often report that they don't respond to the types of

medication that relieve other people's pain.

New research from the University of Michigan Health System helps to

explain why that might be: Patients with fibromyalgia were found to

have reduced binding ability of a type of receptor in the brain that

is the target of opioid painkiller drugs such as morphine.

The study included positron emission tomography (PET) scans of the

brains of patients with fibromyalgia, and of an equal number of sex-

and age-matched people without the often-debilitating condition.

Results showed that the fibromyalgia patients had reduced mu-opioid

receptor (MOR) availability within regions of the brain that

normally process and dampen pain signals -- specifically, the

nucleus accumbens, the anterior cingulate and the amygdala.

" The reduced availability of the receptor was associated with

greater pain among people with fibromyalgia, " says lead author

E. , Ph.D., research investigator in the Division of

Rheumatology at the U-M Medical School's Department of Internal

Medicine and a researcher at the U-M Chronic Pain and Fatigue

Research Center.

" These findings could explain why opioids are anecdotally thought to

be ineffective in people with fibromyalgia, " he notes. The findings

appear in The Journal of Neuroscience. " The finding is significant

because it has been difficult to determine the causes of pain in

patients with fibromyalgia, to the point that acceptance of the

condition by medical practitioners has been slow. "

Opioid pain killers work by binding to opioid receptors in the brain

and spinal cord. In addition to morphine, they include codeine,

propoxyphene-containing medications such as Darvocet, hydrocodone-

containing medications such as Vicodin, and oxycodone-containing

medications such as Oxycontin.

The researchers theorize based on their findings that, with the

lower availability of the MORs in three regions of the brains of

people with fibromyalgia, such painkillers may not be able to bind

as well to the receptors as they can in the brains of people without

the condition.

Put more simply: When the painkillers cannot bind to the receptors,

they cannot alleviate the patient's pain as effectively,

says. The reduced availability of the receptors could result from a

reduced number of opioid receptors, enhanced release of endogenous

opioids (opioids, such as endorphins, that are produced naturally by

the body), or both, says.

The research team also found a possible link with depression. The

PET scans showed that the fibromyalgia patients with more depressive

symptoms had reductions of MOR binding potential in the amygdala, a

region of the brain thought to modulate mood and the emotional

dimension of pain.

The study subjects were 17 women with fibromyalgia and 17 women

without the condition.

The senior author of the paper was Jon-Kar Zubieta, M.D., Ph.D., the

Phil F. Research Professor of Depression in the U-M

Department of Psychiatry and a member of U-M's Molecular and

Behavioral Neuroscience Institute, Depression Center and Department

of Radiology. Other authors were J. Clauw, M.D.; J.

, Ph.D.; A. McLean, M.D., MPH; and H. Gracely,

Ph.D.

The research was supported by grants from the Department of the

Army; the National Center for Research Resources, a component of the

National Institutes of Health; and the NIH. was supported by

an NIH--National Center for Complementary and Alternative Medicine

Grant. McLean was supported by an NIH grant.

Reference: The Journal of Neuroscience, Sept. 12, 2007, 27(37):10000-

-10006.

Note: This story has been adapted from a news release issued by

University of Michigan Health System.

Read Original Article

© 2007 Science Daily