Coated low-dose aspirin may be less potent at preventing blood clots that can cause heart attacks and strokes than plain aspirin, according to a new study.
At the low 75 mg dose, plain uncoated aspirin resulted in significantly lower levels of serum thromboxane, the chemical that causes blood platelets to stick together, than any of three brands of enteric-coated aspirin.
Clinical studies have shown that aspirin lowers the risk of heart attacks, strokes and angina in people at risk for heart disease through anti-inflammatory and anti-clotting mechanisms.
But because aspirin is known to cause stomach ulcers, low-dose coated aspirin is most often recommended.
"At the low doses of 75 milligrams, a significant percentage of people are not receiving sufficient aspirin," says Dermot Cox, lecturer in the department of clinical pharmacology at the Royal College of Surgeons in Dublin. "This is a problem particularly for overweight patients."
Coated aspirin is absorbed in the colon rather than the stomach, and it may take a little more to get therapeutic results, especially in larger people.
But those who take aspirin to help prevent heart disease should not change their dose without checking with their doctors, urges Dr. Richard Stein, a spokesman for the American Heart Association.
"This study indicates you have three options to consider, particularly if you weigh 180 pounds or more: remain on your current dose, go to 162 mg, what we commonly call 'baby aspirin,' or go to uncoated 81 mg aspirin," he says. "You need to talk with your doctor about which would be least likely to cause irritation or other problems."