July 10, 2015 -- Popular painkillers like ibuprofen and naproxen have carried warnings for years about potential risks of heart attacks and strokes. This week, the FDA decided to strengthen those warnings on the medications, known as nonsteroidal anti-inflammatory drugs, or NSAIDs.

The warning includes both prescription and over-the-counter versions of drugs. It emphasizes that the risk applies to even short-term use of medications like Advil, Aleve, and Motrin. And it’s true for people with or without heart disease.

After looking at new safety information on both forms of the drugs, the FDA determined that the risks are greater than originally believed. The risk of heart attack and stroke can happen even in the first few weeks of using the drugs. And that risk is greater the higher the dose. These worse odds apply to people with or without a history of heart disease, the FDA says.

"They are not ruling out risk on a short-term basis," says Bill McCarberg, MD, a San Diego family physician who has published extensively on NSAIDs. The new warning, he says, "lets even occasional users know they are taking a risk."

While some NSAIDs may be less risky, the agency says the information it has now is not enough to rate individual drugs by risk level.

"It has to do with how the medicines interact with the platelets," McCarberg says. Platelets are blood cells that help the blood clot and prevent bleeding.

The non-aspirin NSAIDs work in a different way than aspirin, says Mark Creager, MD, president of the American Heart Association.

"Aspirin as we know from many, many studies, is protective against heart attacks," he says. Aspirin blocks an enzyme that prevents platelets from clumping together and forming dangerous clots that can block a vessel and cause a heart attack or stroke. The non-aspirin NSAIDs work on that enzyme, too, but also affect another enzyme that promotes clotting. That can lead to heart attacks and strokes.