Why Don't My Pain Meds Work?
Fibromyalgia patients often have to fight the notion that they are hypochondriacs. One reason people fail to believe that the pain of fibromyalgia is real is due to the fact that fibromyalgia patients report they don't obtain relief from typical pain medications that are so effective for others. The fact that such logic is faulty is scant comfort to fibromyalgia sufferers, who not only have to bear their pain but also the disdain of others.
Now there's hope that some new light can be shed on why pain medications don't help fibromyalgia patients and this may help lend some credibility to those who have the condition. The University of Michigan Health System found that the receptors in the brains of fibromyalgia patients have a decreased binding ability in response to morphine and other opioid pain killers.
The study used 17 female participants with fibromyalgia and 17 women without fibromyalgia, all of a similar age, and subjected them to positron emission tomography (PET) brain scans. It was found that the mu-opiod receptor (MOR) of the women with fibromyalgia had reduced availability in the areas of the brain that analyze and alleviate pain signals, in particular, the amygdala, the anterior cingulate, and the nucleus accumbens.
Lead author Richard E. Harris, 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 reported in The Journal of Neuroscience, that the lesser availability of the receptor was linked to increased levels of pain among the fibromyalgia patients. Says Harris, "These findings could explain why opioids are anecdotally thought to be ineffective in people with fibromyalgia. 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 must bind to opioids receptors located in the central nervous system in order to be effective. Such drugs include morphine, codeine, drugs containing propoxyphene such as Darvocet, drugs containing hydrocodone for instance Vicodin, and oxycodone medications like Oxycontin.
The researchers hypothesize that fewer available MORs cause the failure of the painkillers to bind to the receptors in the brains of fibromyalgia sufferers, leading to the ultimate ineffectiveness of these drugs in alleviating the chronic pain of these patients.
An intriguing aspect of this study is the finding of a possible link between the ineffectiveness of opioids on fibromyalgia patients and depression. PET scans showed that those fibromyalgia patients who had the greatest number of depressive symptoms had fewer MORs available in the amygdala, the emotion control center of the brain.