When Drugs Give Unexpected Benefits
The blood thinner warfarin recently was found to help ward off cancer in people treated for blood clots. The same week, three studies suggested that popular cholesterol-lowering drugs called statins may somehow reduce the risk of broken bones.
Huh? This sort of pharmaceutical serendipity is increasingly common: A drug approved for one use is found, by accident or design, to have other intriguing effects. It’s distracting to health consumers already teetering on the risk-benefit balance beam.
Should a woman worried about osteoporosis consider taking statins, which are approved only against high cholesterol? Does it make sense for anyone without blood clots to start taking warfarin (brand name: Coumadin) on the chance it could lessen the risk of cancer?
Not yet, experts agree.
“I don’t think anybody in their right mind would start taking Coumadin for this [anticancer] effect,” said Raymond Woosley, chairman of pharmacology at Georgetown University Medical Center. The evidence for its ability to prevent cancer falls short of proof, he said, and the drug is not without serious side effects, including bleeding. It can cause ulcers and, in rare cases, stroke.
Nor should people take statins for a possible preventive effect against osteoporosis, Woosley said. Although they are relatively safe, statins (brand names: Lescol, Lipitor, Mevacor, Pravachol, Zocor) also have potential side effects, including muscle and kidney damage.
“These are exciting leads,” Woosley said of the warfarin and statin findings. But where they lead, he added, depends on whether the initial data are confirmed by more-elaborate cause-and-effect studies.
Whether those studies will be done is another question. Companies are reluctant to undertake such expensive studies in a drug such as Coumadin, whose patent has expired, Woosley said. They are more likely to focus on a similar but newer drug, whose approval for the new use would be much more lucrative.
In the warfarin study, Swedish researchers followed 854 patients treated for blood clots blocking blood flow in the legs or lungs. Half were given warfarin for six weeks, and half for six months. During the next six years, cancer was diagnosed in 16% of the patients who got the drug briefly, but only 10% of those who got it longer.
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No one knows why blood clots might put people at higher risk of cancer, or why a blood thinner might help prevent cancer, or whether the apparent link is a statistical fluke--the mischief of some still-unidentified confounding factor.
“Our findings strongly support the impression that warfarin has an [anticancer] effect, but this idea will remain controversial in the absence of a demonstrated biochemical explanation,” the Swedish researchers noted in the New England Journal of Medicine.
An accompanying editorial said it’s premature for cancer patients and others at high risk of cancer to start taking blood thinners. “For now,” it said, “the answer must be no.”
Doctors voiced a similar caution about the tantalizing evidence that statins might, in addition to lowering cholesterol, somehow protect against osteoporosis. Two of the studies appeared in the Journal of the American Medical Assn., and a third in the Lancet.
“If [statins] do have this additional benefit, that’ll be great, but I’d like to have more evidence,” said Conrad Johnston Jr., an endocrinologist and president of the National Osteoporosis Foundation. Detailed longer studies that directly test statins against osteoporosis are needed to make sure the apparent link is more than a coincidence, he said.
“We have good drugs for osteoporosis,” Johnston said. “I’d use the statins for what they’re designed for--heart disease, which kills a lot of people.”
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An editorial in JAMA called the statin findings “a reminder that drugs that influence fundamental cellular processes often are developed for one system or condition and are later found to have major, unanticipated effects on other systems and diseases.”
The testing that the Food and Drug Administration relies on in approving drugs for marketing naturally focuses on whether the drugs are safe and effective for a particular use. Such testing “imperfectly predicts the various clinical effects of their long-term use in clinical practice,” the editorial noted.
“When a drug goes on the market, we learn an awful lot more about it--some good, some bad,” Woosley said. “These are foreign chemicals put in a body that can react in all kinds of ways.”
