The heart-protective benefits of buffered aspirin may be concealed by its special coating, according to a study published Tuesday in the journal Circulation, a factor that could lead doctors to unnecessarily prescribe stronger, more expensive medicine.
The conclusion about coated aspirin was only one finding in the study, the main goal of which was to test for the prevalence of a hotly disputed phenomenon known as "aspirin resistance," or the idea that aspirin in general doesn't help prevent heart attacks or stroke in some people.
For more than a decade, cardiologists and drug researchers have posited that anywhere from 5 percent to 40 percent of the population is aspirin-resistant, but some prominent doctors have complained that the condition's prevalence has been exaggerated by testing firms and drug makers with a commercial interest in proving that aspirin doesn't always work.
The new study's authors, from the University of Pennsylvania, contend that they did not find a single case of true aspirin resistance in any of 400 healthy people who were examined. Instead, they say, the buffered coating on aspirin interfered with the way the drug entered the body, making it appear as if the drug wasn't working. The study was funded partially by Bayer, one of the world's largest manufacturers of brand-name, buffered aspirin.
There is little evidence that buffered aspirin protects the stomach better than uncoated aspirin, said University of Pennsylvania pharmacology department chairman Garret FitzGerald, one of the study's authors. "These studies question the value of coated, low-dose aspirin," he said in a statement accompanying the article. "This product adds cost to treatment, without any clear benefit."
In a statement, Bayer took issue with some of the study's conclusions and methods, noting that it looked only at healthy volunteers, not at patients in the real world, and said previous studies of coated aspirin have been shown to stop blood platelets from sticking together -- which can help prevent heart attacks and stroke -- at levels comparable to uncoated aspirin.