The warning follows recent studies linking two prescription arthritis drugs, Vioxx and Celebrex, to cardiovascular problems.
Naproxen was part of a study by the National Institutes of Health (NIH). The study was investigating whether naproxen or the arthritis drug Celebrex could be used to treat Alzheimer's disease. NIH researchers halted the survey after finding people who took naproxen were 50 per cent more likely to have heart attacks or strokes.
"This step is being taken as a precautionary measure to ensure the safety of the study's participants," said Elias A. Zerhouni, NIH Director. "The investigators made their decision based on the risk/benefit analysis specific to this trial," he added.
The FDA advised patients taking over-the-counter naproxen products to follow the instructions on the label and not to exceed the recommended dose (220 milligrams twice daily).
The findings came more than two months after drug manufacturer Merck recalled a similar arthritis drug, Vioxx, after similar results. Merck now faces hundreds of lawsuits and potentially billions of dollars in damages.
Naproxen and Celebrex are in a group of drugs called non-steroidal anti-inflammatory drugs (NSAID), which include aspirin and ibuprofen. Within that group, Vioxx and Celebrex are part of a class known as Cox-2 inhibitors, along with Pfizer's Bextra.
Naproxen is sold as a generic and under several brand names, including Bayer AG's Aleve, and as Roche AG subsidiary Roche Palo Alto's Naprosyn.
In 2003 Roche were the biggest sellers in the small subsector of naproxen painkillers. Although naproxen sales are relatively small, combined Bayer-Roche sales amount to $1.3 billion (€970 million) making it the best-selling NSAID in the US.