A new clinical trial has linked propoxyphene use with a higher risk of developing serious and sometimes fatal heart rhythm abnormalities due to changing electrical activity in the heart. The FDA says that the maker of brand versions Darvon and Darvocet, Xanodyne Pharmaceuticals has agreed to withdraw their prescription medications from the US market; something the FDA (Food and Drug Administration) had asked them to do.

The FDA says it is communicating with generic makers of medications that contain propoxyphene, informing them of Xanodyne's decision and asking them also to voluntarily remove their products.

The FDA says new information, including epidemiological data, shows that the risks of taking propoxyphene-containing medicines probably outweigh the benefits.

John Jenkins, M.D., director of the Office of New Drugs in the FDA's Center for Drug Evaluation and Research (CDER), said:
    "The FDA is pleased by Xanodyne's decision to voluntarily remove its products from the U.S. market. These new heart data significantly alter propoxyphene's risk-benefit profile. The drug's effectiveness in reducing pain is no longer enough to outweigh the drug's serious potential heart risks."
Physicians should stop prescribing propoxyphene. Anybody currently taking propoxyphene-containing medications should see their doctor immediately so they can talk about switching to another pain medication.

Propoxyphene, an opioid, has been used for the management of mild to moderate pain. It was approved in the USA in 1957.

Despite receiving two requests since 1978 to get propoxyphene-containing drugs off the shelves, the USA had decided that the benefits outweighed the risks; but not anymore.

In January 2009, an FDA Advisory Committee voted 14 to 12 to withdraw marketing authorization of propoxyphene products. Further information regarding risks and benefits related to cardiac effects would be useful, the Committee commented at the time.

In the European Union, a phased withdrawal has been underway for some time, since the EMEA (European Medicines Agency) recommended pulling propoxyphene form the market.

In July 2009, the FDA allowed the continued sale of propoxyphene, but asked for a new boxed warning to be added to its labeling, alerting doctors and patients of a fatal overdose risk. The Agency also asked Xanodyne to carry out a new safety study, specifically focusing on its effects on the heart.

The FDA has concluded, after reviewing new data, that even at recommended doses, propoxyphene causes considerable changes to the heart electrical activity, which can be viewed on an ECG (electrocardiogram). A change in the heart's electrical activity can cause serious heart problems, including sudden death.

Gerald Dal Pan, M.D., M.H.S., director of the Office of Surveillance and Epidemiology, CDER, said:
    "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. 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."
Source: FDA

Written by Christian Nordqvist