Xanodyne Pharmaceuticals, which makes 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 (FDA).
The FDA has also informed generic drug manufacturers of Xanodyne's decision, and they will be removing their propoxyphene-containing products from the market as well.
Propoxyphene is an opioid used to treat mild to moderate pain. First approved by the FDA in 1957, it is sold by prescription under various names both alone (Darvon) or in combination with acetaminophen (Darvocet).
Since 1978, the FDA has received two requests to remove propoxyphene from the market. Until now, the FDA had concluded that the benefits of propoxyphene for pain relief at recommended doses outweighed the safety risks of the drug.
In June 2009, the European Medicines Agency recommended that the marketing authorizations for propoxyphene be withdrawn across the European Union. A phased withdrawal of propoxyphene is under way.
In July 2009, the FDA required Xanodyne to conduct a new safety study assessing unanswered questions about the effects of propoxyphene on the heart. The agency now has reviewed the data from that study, which 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, can increase the risk for serious abnormal heart rhythms that have been linked to serious adverse effects, including sudden death.
As a result of these data, combined with other information, including new epidemiological data, the FDA concluded that the risks of the medication outweigh the benefits.
"These new heart data significantly alter propoxyphene's risk-benefit profile," said John Jenkins, MD, director of the Office of New Drugs in the FDA's Center for Drug Evaluation and Research (CDER). "The drug's effectiveness in reducing pain is no longer enough to outweigh the drug's serious potential heart risks."
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.
"With the new study results, for the first time we now have data showing that the standard therapeutic dose of propoxyphene can be harmful to the heart," said Gerald Dal Pan, MD, MHS, director of the Office of Surveillance and Epidemiology at CDER. "However, long-time users of the drug need to know that these changes to the heart's electrical activity are not cumulative. Once patients stop taking propoxyphene, the risk will go away."
The FDA is advising healthcare professionals to stop prescribing propoxyphene to their patients, and patients who are currently taking the drug should contact their healthcare professional as soon as possible to discuss switching to another pain management therapy.
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