Xanodyne Pharmaceuticals Inc. the maker of Darvon and Darvocet, the brand version of the prescription pain medication propoxyphene, has agreed to withdraw the medication from the U.S. market at the request of the U.S. Food and Drug Administration. The FDA also informed the generic manufacturers of propoxyphene-containing products of Xanodyne’s decision and requested that they voluntarily remove their products as well. The FDA sought market withdrawal of propoxyphene after receiving new clinical data showing that the drug puts patients at risk of potentially serious and even fatal heart rhythm abnormalities. As a result of the data and other information, the FDA decided that the risks of the medication outweigh the benefits. Studies show that, even when taken at recommended doses, propoxyphene causes significant changes to the electrical activity of the heart. These changes, which can be seen on an electrocardiogram (ECG), can increase the risk for serious abnormal heart rhythms that have been linked to serious adverse effects, including sudden death. The available data also indicate that the risk of adverse events for any particular patient (even patients who have taken the drug for many years) is subject to change based on small changes in the health status of the patient, such as dehydration, a change in medications, or decreased kidney function.