A decade’s worth of research on nonsteroidal anti-inflammatory drugs, or NSAIDs, has prompted the Food and Drug Administration to demand stiffer warnings on the labels of such prescription medications as celecoxib (marketed commercially as Celebrex) and diclofenac (Voltaren) about the increased risk of heart attacks and strokes in those taking the drugs.

Prescription NSAID labels now will alert consumers that the higher risk of stroke or heart attack is evident in the first weeks a patient starts taking such drugs, that the risk appears to escalate at higher doses and with longer use, and that even people with no other cardiovascular risk factors are more likely to suffer heart attack or stroke when taking the medications.

The warnings will also note for the first time that using NSAIDs increases a person’s likelihood of suffering heart failure and that in their first year after a heart attack, patients treated with such medications were more likely to die than heart attack victims who did not take them.

The FDA said Thursday that for now, only prescription NSAIDs would be required to add the warnings. But the agency said it would soon ask the manufacturers of over-the-counter NSAIDs such as ibuprofen (Advil, Motrin) and naproxen (Aleve) also to update their labels to reflect the stiffer warnings.

Those warnings come a decade after the FDA issued a public health advisory on the use of rofecoxib, better known as Vioxx, after it was found that those taking the medication had higher rates of heart attack and stroke. The pharmaceutical giant Merck subsequently pulled Vioxx from the market.

Several months later, the agency directed that all NSAIDs should carry a boxed warning on their labels alerting consumers to a “potential increased risk of serious adverse (cardiovascular) events.” The FDA also asked Pfizer, manufacturer of a widely prescribed NSAID called Bextra to pull its product off the market.

The new language comes in the wake of renewed scrutiny by the agency of a class of drugs taken by millions of Americans for occasional aches and pains, and widely used to treat chronic conditions such as arthritis. In February 2014, the FDA convened a meeting of two of its advisory panels—one that specializes in arthritis treatment and one that focuses broadly on drug safety — to consider whether new research warranted a change in warnings to consumers.

Not all of the new warnings clarify NSAIDs’ risks for consumers.

Among the new language to appear on NSAIDs’ labels is a statement hinting that not all NSAID medications carry equal risk of heart attack and stroke, suggesting that consumers might be able to shift from their anti-inflammatory pain medication to another, safer one.

But the FDA warning cautions that “this newer information is not sufficient for us to determine that the risk of any particular NSAID is definitely higher or lower than that of any other particular NSAID.”

That inconclusive advice came after the FDA advisory panels considered the findings of three published studies – all meta-analyses – that found patients taking naproxen had fewer heart attacks and strokes than those taking ibuprofen or celecoxib. In the end, the panel accepted critics’ arguments that such studies could not support claims of naproxen’s safety, and recommended against making such distinctions on medications’ labels.

Although it cautions that even patients with no cardiovascular risk factors increase their risk when taking NSAIDs, the new warnings do underscore that patients with heart disease or risk factors for it are more likely to have a heart attack or stroke, “because they have a higher risk at baseline.”