U.S. Doctors Identify Treatment for Severe, Chronic Pain
Relief from agonizing chronic pain appears to be on the way for people who have had serious injuries or with diseases such as cancer, AIDS and diabetes, according to researchers.
A Dartmouth Medical School study of laboratory rats found that neuropathic pain, which is impervious to traditional painkillers, can be inhibited by blocking the action of small bodily proteins called cytokines in the central nervous system.
The study results were presented at the annual meeting of the American Assn. for the Advancement of Science in Philadelphia last week.
“We may be on the verge of a new pharmacopeia for preventing and treating pain,” said Joyce DeLeo, the Dartmouth professor of anesthesiology and pharmacology who led the study.
Neuropathic pain can afflict people who have been hurt in car crashes, had surgery or suffer major chronic illnesses. What has baffled scientists until now is that the burning or “shooting” sensations of neuropathic pain can intensify after the healing process has been completed.
Researchers say neuropathic pain is more common than Alzheimer’s disease. In more than half of all sufferers, the disorder manifests itself as chronic lower back pain.
“This is very severe pain that can last for 10 years--every day, all day long and all night long,” said Dr. Gary Bennett of Allegheny University. “You don’t get a vacation.”
Research shows that cytokine protein cells, normally associated with the body’s immunity, are produced in the central nervous system in large numbers as a consequence of peripheral nerve damage.
Opiates including morphine are ineffective against pain resulting from that condition.
If cytokine activity were held in check by new treatments, doctors say, traditional painkillers could then be used to control discomfort.
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The new treatments can be expected within five years, possibly sooner.
Bennett said three drug families have proved effective against neuropathic pain in early human trials.
They are: the antiepilepsy drug gabopentin; an experimental class of antiepilepsy drugs called N-Methyl-D-Aspartate receptor blockers; and substances called conopeptides, which originate from the venom of poisonous snails and have been synthesized by Neurex Corp. in the form of a drug called SNX-111.
“Every major drug company in the world is working on NMDA receptor-blockers,” Bennett said.
Studies of neuropathic pain suggest an underlying connection between the body’s immune and central nervous systems, which up to now have been thought to operate independently.
Researchers have been able to reproduce hypersensitivity to temperature and touch in rats by injuring a single nerve cell. Scientists find that a persistent barrage of nerve signals from the site of tissue or nerve damage can heighten the perception of pain and alter the way the entire nervous system functions. DeLeo said further study of cytokines is necessary.
“Cytokines are a double-edged sword, with both beneficial and destructive actions,” she said. “To tailor effective treatments, we will need to learn more about the timing and balance of these powerful immune proteins.”
