• 1/17/2006
  • Fort Wayne, IN
  • Lauran Deergaard
  • FortWayne Journal Gazette (fortwayne.com)

The dog hopped on three legs, pain from bone cancer so bad that he wouldn’t let his afflicted fourth paw touch the floor. His owner was bracing for euthanasia when scientists offered a novel experiment: They injected a fiery sap from a Moroccan plant into Scooter’s spinal column – and the dog frolicked on all fours again for several months.

The chemical destroyed nerve cells that sensed pain from Scooter’s cancer, not helping the tumor but apparently making him no longer really feel it.

The dramatic effect in dogs has researchers from the National Institutes of Health preparing to test the chemical in people whose pain from advanced cancer is unrelieved by even the strongest narcotics.

The first human study could begin by next year, at the NIH’s Bethesda, Md., hospital. A second study in pain-ridden dogs is slated for this summer at the University of Pennsylvania.

If the research pans out, it might one day offer doctors, and veterinarians, a desperately needed new approach to attack intractable pain. And it’s from an unlikely source, a more potent cousin of the chemical that makes chili peppers hot.

Why would a substance that feels like it’s burning a hole in your tongue – yes, one researcher tasted it – relieve pain, too?

This fiery chemical, called resiniferatoxin or RTX, can poison certain nerve cells that control a type of heat-related, inflammatory pain, apparently eliminating one of the body’s pain-sensing systems. Yet it doesn’t seem to harm other nerves that sense, say, the sharp pain from stepping on a tack.

“The beauty of this is it just selectively targets,” said Dr. Andrew Mannes, an NIH anesthesiologist who specializes in pain management.
“If you live a long time, you need all your pain systems. There are people on morphine drips with really no other option. (Eliminating one) seems like a good trade.”

The discovery led government scientists to scour the hillsides of Morocco for the cactus-like plant and take the unusual step of essentially manufacturing an experimental drug from its sap.
Narcotics called opioids, such as morphine, are the mainstay of treatment for pain from late-stage cancer. But between 5 and 15 percent of patients – anywhere from 40,000 to 100,000 Americans a year, Mannes estimates – don’t get relief.