Aspirin advice: Coated vs. plain

Ask the doctor


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Q. Ever since my heart attack, I've been taking a daily low-dose aspirin. I usually buy enteric-coated aspirin to reduce my risk of a stomach ulcer, but I read that coated aspirin may not be as effective as plain aspirin. What do you recommend?

A. Much of the aspirin sold in the United States is enteric-coated. Sometimes referred to as safety-coated, these smooth pills are designed to withstand stomach acid and pass through the stomach before fully dissolving in the small intestine (enteric comes from the Greek word for intestine).

All aspirin blocks substances that protect the cells lining the stomach, which increases the risk of bleeding there. Although enteric-coated aspirin might lead to less stomach irritation, the covering has not been proven to lower the risk of aspirin's most common worrisome side effect — bleeding in the stomach or intestines. No matter where aspirin dissolves, the drug gets into the bloodstream, and once there, it interferes with blood clotting (which is why it helps prevent heart attacks).

Also, it is possible that the coating might make aspirin slightly less effective in certain situations. Some research suggests that for certain people, the coating interferes with the ability to absorb the medicine. However, because the drug's anti-clotting effect lasts for more than just one day, slight variations in day-to-day absorption might not matter all that much, assuming a pill is taken every single day. Plain, low-dose (81-mg) aspirin (which also comes in orange and cherry flavors) may be a better option, especially for people who tend to miss a dose now and then.

It's important to note that the decision to take a daily low-dose aspirin should always be made with a doctor. For people like you, who have already had a heart attack or certain forms of stroke, the answer is usually yes. For everyone else, the decision will depend on their age, sex, and risk of heart disease and bleeding. A free app called Aspirin Guide (available for Apple and Android devices) can assess a person's risk in seconds during a routine doctor's visit and emails both doctor and patient a summary of the decision-making process.

To help avoid stomach irritation while taking low-dose aspirin, you can take it with a meal or snack. Drugs to treat heartburn, including simple antacids like Tums, acid blockers like famotidine (Pepcid, Fluxid, generic), or proton-pump inhibitors (PPIs) such as omeprazole (Prilosec, Zegerid, generic) may also help protect your stomach. But you should check with your doctor first, especially if you are taking other medications.

One final note: If you suspect you're having a heart attack, doctors recommend chewing one full-strength (325-mg) aspirin or four low-dose aspirin, right after you call 911. This way the aspirin gets into your bloodstream much more quickly to help prevent clots than it would if you swallowed it.

— by Deepak L. Bhatt, M.D., M.P.H.
Editor in Chief, Harvard Heart Letter