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 ba
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