FRIDAY, Nov. 19 (HealthDay News) -- The opioid-based painkillers Darvon and Darvocet are being withdrawn from the U.S. market because they've been linked to serious and potentially deadly heart rhythms, federal officials said Friday.

The U.S. Food and Drug Administration said Xanodyne Pharmaceuticals -- which makes Darvon and Darvocet -- is voluntarily taking the drugs off the market. The active ingredient in these drugs is propoxyphene. The agency has also asked the makers of generic versions of propoxyphene to remove them from the market.

"We have recently completed our review of a new clinical trial that was designed to assess the impact of propoxyphene on the electrical activity of the heart," Dr. John Jenkins, director of FDA's Office of New Drugs, Center for Drug Evaluation and Research, said during a Friday press conference. The trial showed propoxyphene can cause potentially serious or even deadly heart rhythm problems, called arrhythmias, he said.

"We concluded the pain benefits of propoxyphene no longer outweighed the heart risk and that propoxyphene should no longer be sold in the United States," Jenkins said.

In 2009, the European Medicines Agency recommended withdrawing the drug across the European Union. A phased withdrawal is under way, the FDA said.

Dr. Gerald Dal Pan, director of the FDA's Office of Surveillance and Epidemiology, said the agency is asking doctors to stop prescribing propoxyphene.

"We are advising patients who are currently taking the drug not to stop taking propoxyphene right away. You still need to manage your pain. Instead, we urge you to contact your health care professional as soon as possible to discuss switching to another pain-management therapy," he said.

Dal Pan said patients taking the drug who experience heart palpitations, dizziness or light-headedness should contact their doctor right away.

People who stop the drug suddenly may experience withdrawal effects, such as nausea, diarrhea, anxiety and shivering, he said. "That's why this should be done under the supervision of a medical professional," he added.

Dal Pan said that the heart effects of propoxyphene aren't cumulative, so once the drug is stopped the risk should go away.

In 2009, approximately 10 million people in the United States were taking propoxyphene, he said. The most widely prescribed version was Darvocet, he noted.

Propoxyphene was approved by the FDA in 1957, is sold by prescription under various names, including Darvon, or in combination with acetaminophen (Darvocet).

The FDA said it had been asked twice since 1978 to take propoxyphene off the market, but until now the agency believed the drug's benefits outweighed the risks.

In 2009, an FDA advisory committee voted 14 to 12 to remove the drug from the market.

Despite that 2009 recommendation, the FDA left the drug available, but required a new boxed warning on the label, alerting patients and doctors of the risk of a fatal overdose. The agency also required Xanodyne to conduct a new safety study of propoxyphene's impact on the heart.

Results of that study showed significant changes to the heart's electrical activity, which can increase the risk for serious abnormal heart rhythms that have been linked to serious adverse effects, including sudden death, the FDA said.

In a news release issued after the FDA announcement, Dr. Sidney Wolfe, director of Public Citizen's Health Research Group, said: "The announcement by the U.S. Food and Drug Administration that propoxyphene-containing products are finally going to be taken off the market -- because of dangers previously known and acted upon, with bans announced in the U.K. almost six years ago, and in Europe, almost 1.5 years ago -- is a serious indictment of the FDA's long-lasting unwillingness to protect people in this country from a deadly but barely effective painkiller."

Dr. William O'Neill, executive dean for clinical affairs at the University of Miami Miller School of Medicine, said he had a problem with the way the FDA handled drug withdrawals, recalls and warnings.

"I'm a little annoyed, because what always happens with these drug recalls is that they tell patients to see their doctor, which puts the onus on doctors to help each individual patient make a decision about the benefit of the drug versus the potential side effects," O'Neill said.

Practicing physicians have no basis to make an informed decision, because they have not seen that data on which the FDA made its decision, O'Neill said. "I have no way of getting that information; it's not in any published journal," he said. "I have to infer from the nanny state that this is what's best -- I know what's right -- without being able to determine whether the drug is of value or not."

More information

For more on pain medications, visit the U.S. National Library of Medicine.