April 14, 2000 (New York) -- Researchers seeking new ways to relieve the pain that persistently plagues many Americans are looking in some unusual places: a snail found in the Philippines, a poisonous frog from Ecuador, and the marijuana plant.
According to a recent Gallup survey, pain is a fact of life for many in the U.S., with 46% of women and 37% of men reporting that they experience some pain daily. Pain can be acute, or short-lived, like that experienced after an accident; or chronic, meaning it lasts long after an injury has healed or is due to persistent inflammation or nerve damage. Some diseases, such as diabetes and shingles, can cause long-term pain that is difficult to treat.
Several types of pain medication are now commonly used, but all have drawbacks. Nonsteroidal anti-inflammatory drugs, or NSAIDS, and the anti-inflammatory drug Tylenol are used for milder pain. But they don't work on all types of pain, and some may result in side effects such as bleeding in the intestinal tract. For more severe pain, doctors may give narcotics, which can cause problems such as slowed breathing and constipation, and which can also be addictive with prolonged use. This has led researchers to look for drugs that have the same actions without the side effects.
A review in the April issue of Nature Biotechnology describes research that is uncovering how pain is eased and that is leading to the development of drugs from marijuana, peppers, snails, and frogs that target particular pain-production centers in the body, among other things.
One area of research involves the marijuana derivatives called cannabinoids. Like narcotics such as morphine and codeine, cannabinoids interfere with the area of the brain that perceives pain. Research at the University of California in San Francisco suggests that cannabinoids are more effective than opioids for some types of chronic pain. But cannabinoid research is controversial, and researchers are focusing on separating the compound's useful characteristics from the euphoric properties that make marijuana attractive to drug abusers.
Peppers are another hot area of pain research. Investigators treating patients with overactive bladders and a diabetes-related condition in which people experience pain in their extremities are working with a derivative of capsaicin, the main ingredient in hot peppers. Capsaicin itself is a pain reliever, but researchers say the derivative seems to have fewer side effects.
The lowly snail is making headlines, too, with reports that venom from the cone snail, which lives on the coast of the Philippines, is a potent drug for relieving pain after surgery and some types of chronic pain. Researchers at Johns Hopkins University and elsewhere have used a compound from the venom -- and say it is a thousand times more potent than morphine, and an option for very ill patients who do not respond to morphine.
Then there is the poisonous Ecuadorian frog known as Epipedobates tricolor, which secretes a substance on its skin to kill predators. The substance possesses pain-relieving properties hundreds of times more potent than morphine, but is too poisonous for human use. The drug company Abbott Laboratories has developed a synthetic version of the substance that is being tested for both acute and chronic pain.
A promising treatment for diabetes-related pain is a drug known as Prosaptide TX14A, developed by John S. O'Brien, MD, a professor of neuroscience at the University of California in San Diego. Myelos Neuroscience of San Diego has completed early tests of the drug in 150 patients.
"We saw very good efficacy results and very good safety results with no significant adverse events," Robert Schuessler, director of clinical and regulatory affairs at Myelos, tells WebMD. The company believes the daily injection works on the underlying cause of the pain, but stresses that this is a theory based on animal testing. If future studies confirm the safety and efficacy of the drug, the company plans to file an application for approval with the FDA.
Some researchers are also looking at ways to use gene therapy to deliver drugs to specific pain sites in the body. And, there is hope that new methods of diagnosing the specific cause of an individual's pain will soon be available, allowing doctors to use that information in selecting pain-killing drugs.
- Current therapies used to treat pain include drugs that suppress inflammation, which work for mild to moderate pain, or narcotic agents, which can be addictive.
- With so few choices for treatment, pain is often difficult to treat adequately.
- New research into pain treatments is focusing on compounds from marijuana, hot peppers, snail venom, and secretions from a poisonous frog.