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Aspirin not effective in some people

Failure to take the drug may be the most common reason.

Despite aspirin’s low cost and availability without a prescription, it is a powerful drug: its antiplatelet activity helps prevent clots from forming inside stents or arteries. That’s why people with coronary artery disease who take aspirin have fewer heart attacks and strokes than people who don’t take aspirin.

But aspirin is not fully effective in some people, leaving them vulnerable to a potentially fatal clot. Just how many people are aspirin resistant is unknown: most experts think about 2% of people are resistant, though some estimates are higher.

Diabetes, obesity, smoking, female gender, and history of clots forming inside a stent increase the risk, which is also higher immediately after a heart attack and within 10 days following coronary artery bypass surgery. While some people simply do not respond to aspirin, recent studies suggest that failure to take the medication and inadequate dosing are often at fault.

False reasons for failure

Dr. Christopher Cannon, a cardiologist at Harvard-affiliated Brigham and Women’s Hospital, says the most common reason for aspirin resistance is failure to take the medication. “Nine out of 10 patients will admit they sometimes forget to take their aspirin every day,” he says.

In some others who take aspirin faithfully, the anticlotting effect is not adequate. “We consider these patients aspirin resistant,” says Dr. Cannon. Studies have shown this is relatively rare. It happens more often when taking low-dose aspirin, and raising the dose may overcome the resistance.

What you can do

You may never know whether you are vulnerable to aspirin resistance until you have a problem, because there are no guidelines for when someone should be tested. “We don’t know which test is best, or the number at which we can say resistance starts,” says Dr. Cannon.

It is likely that aspirin does its job 98% of the time. So if you don’t take your daily aspirin as prescribed, you may be taking unnecessary chances with your health.

“Noncompliance with a lifesaving medication could lead you to have a heart attack or stroke, which may be fatal. Aspirin seems like a benign little medication, but it is one of the most important ones to take each day,” Dr. Cannon says.

Posted by: Dr.Health

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