When scientists recently announced results of a study demonstrating that aspirin can reduce the risk of developing colon polyps, the precursor to colon cancer, nobody seemed particularly surprised -- not the medical community nor the public.
After all, people have grown accustomed to aspirin's expanding array of uses from treating heart attacks to preventing certain types of strokes. The old joke about "take two aspirin and call me in the morning" now seems like some of the best medical advice around.
"It's just very rare to find a drug that has contributed so much to the cure of patients," says Dr. Candy Tsourounis, a clinical professor at the University of California at San Francisco School of Pharmacy. "It's really quite amazing."
The accomplishments of this rediscovered wonder drug, acetylsalicylic acid, are made all the more remarkable by its relative simplicity. It's synthesized from a naturally occurring substance, salicin, that can be found in willow tree bark and was prescribed for pain relief as long ago as 400 B.C.
The modern version was invented by a German scientist in 1897 and has been available as a nonprescription drug in the United States for nearly 88 years.
But as simple -- and relatively inexpensive -- as aspirin may be, exactly how it works is not fully understood. One of aspirin's properties is to inhibit the body's production of prostaglandins, hormone-like substances that regulate pain, fever and inflammation.
Researchers speculate that aspirin's effects on prostaglandins may be the reason why it reduces the occurrence of precancerous polyps in the colon. Might that cancer-fighting effect work against other forms of malignancies? Many studies have been launched to answer just that question.
"We really don't know with any certainty how [aspirin] works to prevent polyps from forming in the colon," says Dr. Robert Sandler, who directed the colon cancer study at the University of North Carolina. "We just know that it does."
But that's not the only thing aspirin does to the body. It also has an anti-clotting effect. And that property is thought to be part of the reason why taking a low dose of aspirin daily seems to reduce the chances of having a heart attack as well as certain types of mini-strokes.
"It can be quite effective -- that's been observed for a while now," says Dr. Michael Miller, director of preventive cardiology at the University of Maryland Medical Center.
Miller routinely prescribes low doses of aspirin to his cardiac patients -- 81 milligrams, the same amount as a child's chewable tablet, as a preventive measure. He advises people experiencing chest pains to chew on aspirin (to allow the medication to be absorbed more quickly).
"We give it out like water," he says.
But that has also posed a concern, Miller notes. Aspirin is not without side effects, including stomach ulcers and bleeding. Its blood thinning effects can put certain people at greater risk of a stroke. Patients with an aspirin allergy, asthma, uncontrolled high blood pressure, severe liver or kidney disease or bleeding disorders are generally advised not to take it.
In high doses, it can cause hearing loss or ringing in the ears. Children and teens are often told by doctors not to take it because of aspirin's association with Reye's syndrome, a rare but potentially deadly illness.
Tsourounis, director of a drug information network in San Francisco, says she gets surprisingly few calls from people who want to know more about the side effects of aspirin. "We just don't get people expressing a lot of interest in it," she says.
Physicians worry that more people will choose to self-medicate with aspirin under the assumption that it will extend their lives. Sandler says that hasn't been proved. People who think taking an aspirin is certain to ward off colon cancer, for instance, would be mistaken, he says.
"The message I tell people is the most important thing you can do right now to prevent colon cancer is to be screened," he says. "Taking an aspirin every day may be something people might want to do on top of a colonoscopy."
The Food and Drug Administra-tion recommends that consumers should begin taking an aspirin daily, even the low-dose baby aspirin, only with the advice of a physician.
Recent marketing studies show that aspirin sales have grown nationwide -- at least since 1998 when officials at the FDA rewrote aspirin's prescribing information to include its benefits for victims of heart disease and stroke.
Still, the fact that aspirin is not patented and is manufactured by dozens of different companies means that, unlike newer drugs, no giant multinational pharmaceutical company is promoting its use or, more important, spending large sums to study its efficacy.
That responsibility has fallen on organizations like the National Cancer Institute and the American Heart Association. Scientists say their support is needed, speculating that future research may discover even more powerful effects from a new generation of aspirin-derived drugs.
"Aspirin may be a prototype for a class of compounds," says Dr. Vincenzo Casolaro, an assistant professor of clinical immunology at Johns Hopkins Hospital who has spent years looking at aspirin's effects on prostaglandins. "There's a lot we still don't know."
What is aspirin good for?
Its uses include:
* Treating and preventing transient ischemic attacks, a type of stroke.
* Reducing the risk of a heart attack, preventing recurrent heart attacks and reducing the risk of death when a heart attack is in progress.
* Helping in procedures such as angioplasty and coronary bypass.
* Relieving the symptoms of rheumatoid arthritis and related conditions.
* Reducing the risk of developing precancerous colon and rectal polyps.
-- Peter Jensen
Hippocrates recommends the use of the bark and leaves of willow trees (high in salicin) to counteract pain and fever.
German scientists first experiment with salicin to create salicylic acid.
German company Bayer (a one-time dye maker) sells acetylsalicylic acid in powder form under the name aspirin to doctors to give to their patients. The drug's popularity soars.
First aspirin tablets are sold.
Aspirin is made available over-the-counter.
A California doctor notices a lower rate of heart attacks among patients who take aspirin.
First children's chewable aspirin is marketed.
FDA OKs advertising aspirin for use during a heart attack, and formally recommends it as a way to reduce the risk of death during a heart attack, as a way to prevent recurrent mini-strokes (TIA), and reduce the risk of heart attacks and stroke.
University of North Carolina study shows that patients who have had colorectal cancer may reduce the risk of recurrence by taking one 325-milligram aspirin per day.