Though we may not appreciate it, much of the pain we feel every day is normal and healthy. The intense pain we feel after putting a hand on a hot stove, for instance, tells you that you're doing damage to your body and to move your hand immediately. But neuropathic pain serves no useful purpose - it's the result of damage to nerves that transmit pain signals. And so the nerves send errant, unnecessary pain signals that can put a person in constant, pointless, agonizing pain.
"This type of pain is very abnormal," says Robert Dworkin, Ph.D., the lead author of the guidelines and director of the Anesthesiology Clinical Research Center at the University of Rochester Medical Center. "Many patients worry about how to describe their pain, because it can be so unusual. It seems to come out of nowhere, and it can be excruciating."
Shingles is one of the most common causes of neuropathic pain. For most shingles patients, the painful rash heals in two to three weeks, and the pain is gone permanently. But one in four patients suffers from tremendous pain months or even years after the skin rash heals, because of damage to the nerves, a condition known as post-herpetic neuralgia.
"For many patients who had shingles, just the touch of a shirt or a blouse lightly brushing against the skin can be excruciatingly painful, for years. And so what happens? They stay home, topless. It's hard to go to work, hold a job, or see family and friends if you're sitting home unable to wear a shirt or a blouse. It can truly be disabling," says Dworkin.
Such patients are among the 4 to 6 million people in the United States that Dworkin estimates have neuropathic pain. The group also includes many people with diabetes who can develop a painful condition known as diabetic neuropathy. Such patients might feel extreme pain from just the slightest touch of bed sheets against their feet. Neuropathic pain also affects some patients who have or had cancer, multiple sclerosis, a stroke, a spinal cord injury, or a number of other conditions.
It was just a little more than five years ago that Dworkin pulled together experts from around the world to create the first annual International Conference on the Mechanisms and Treatment of Neuropathic Pain. Then, in late 1998, the Journal of the American Medical Association published two papers on the use of the anti-seizure drug gabapentin to treat pain in patients with diabetes and after shingles. The papers, Dworkin says, stoked the interest of the pharmaceutical industry in neuropathic pain, a condition which had been seen little improvement in treatment for almost two decades.
"When I speak to an audience, I tell them that the lecture I'm going to give about treatment is an entirely different lecture than the one I would have given five years ago," says Dworkin. "The developments have been that rapid."
For most of the past 20 years, doctors treating neuropathic pain have turned to a class of medications known as tricyclic antidepressants, such as amitriptyline. But with recent advances in pain treatment, Dworkin and 20 co-authors recommend five types of medication. In addition to the tricyclic antidepressants, the team recommends gabapentin, originally developed as an anti-seizure medication; a lidocaine patch; narcotics such as oxycontin; and the painkiller tramadol.
"Both patients and doctors need to know that now there are several effective choices when it comes to controlling neuropathic pain," Dworkin says. "These developments are significant; it makes relief possible for some patients who have never before been able to have their pain reduced. Still, there is a whole lot of room for improvement, and research on improved treatments for neuropathic pain is continuing."
The compilation of the guidelines was funded by Endo Pharmaceuticals, a company that makes and sells a lidocaine patch to treat neuralgia following shingles.