Manufacturers of pain-relief medication containing propoxyphene -- such as Darvon and Darvocet -- must emphasize the potential risk for overdose by strengthening warning labels on the drugs, the Food and Drug Administration (FDA) announced July 7.

The FDA also ordered studies to assess propoxyphene's effects on the heart, as well as how often elderly patients are prescribed propoxyphene and the safety profile of propoxyphene compared with other drugs.

Janet Woodcock, M.D, director of the FDA's Center for Drug Evaluation and Research, said that prescribers and patients should be aware of propoxyphene's potential risks, and that physicians should review patient histories carefully and make treatment decisions based on the warning label.

The FDA denied a request from the group Public Citizen for the withdrawal of propoxyphene from the marketplace. saying that despite the FDA's concerns the benefits of using the medication outweigh the safety risks. 

The FDA noted that propoxyphene has been on the market since 1957 and is widely prescribed.