The Food and Drug Administration said Friday that Xanodyne Pharmaceuticals had agreed to halt all U.S. marketing of Darvon and the related brand Darvocet, which have been subject to safety concerns for decades. The Kentucky company confirmed the move in its own statement.
The FDA also called on generic drugmakers to stop marketing low-cost drugs containing the active ingredient in Darvon, called propoxyphene.
Britain and the European Union decided to ban Darvon in 2005 and 2009, respectively, due to a long trend of suicides and accidental overdoses.
FDA officials said they decided to take action based on a recent study showing Darvon interferes with the electrical activity of the heart, causing irregular heart rhythms that can be fatal. Xanodyne conducted the study last year at the government's request.
"This last study, the cardiac study, was sort of the final piece of the puzzle that told us what the complete picture was," said Dr. Gerald Dal Pan, director of FDA's office of surveillance and epidemiology.
Dal Pan said patients should continue taking the medication until their doctor prescribes a replacement therapy. Other commonly-prescribed drugs in the same class are oxycodone and codeine.
But public safety advocates said the agency should have acted much sooner to pull a drug with limited benefits and a long history of safety problems.
"The FDA's deadly delay in this case starkly illustrates how one of the most important public health concepts, the precautionary principle, was embraced by the UK and Europe, but was for too long recklessly rejected by the FDA," said Dr. Sidney Wolfe, of the consumer watchdog group Public Citizen.
Wolfe estimated that at least 1,000 to 2,000 U.S. patients died from taking Darvon since the U.K. banned the product in January 2005.
Public Citizen petitioned the FDA to ban the drug in 1978 and again in 2006, pointing to its role in thousands of deaths reported by state medical examiners.
The most recent petition led to a January 2009 meeting, where a panel of outside experts voted 14-12 to recommend the drug be pulled from the market.
But the FDA disagreed, and later that year agency officials said they would keep the drug on the market with a bolder warning label about the risk of overdosing. Around that time, the FDA asked Xanodyne to conduct the study of the drug's heart effects.
"For the first time we now have data showing that the standard therapeutic dose of propoxyphene can be harmful to the heart," Dal Pan said.
Propoxyphene, which was first approved in the 1957, is an opioid narcotic used to treat mild to moderate pain. About 10 million people in the U.S. received prescriptions for Darvon and related drugs in 2009, according to the FDA.
The most popular form of the drug currently is Darvocet, which combines propoxyphene with the more common painkiller acetaminophen. At FDA's 2009 meeting, officials cited studies showing most of the pain relief from Darvocet came from the acetaminophen component.
Based in Newport, Ky., Xanodyne Pharmaceuticals is a privately-held company focused on pain relief drugs.
A spokesman for the company said it does not advertise Darvon or Darvocet, which make up less than 1 percent of the market for propoxyphene-based drugs. The majority of medicines sold are generic versions, he said.
In the last two years the FDA has begun prodding drugmakers to develop more sophisticated pain relievers that are harder to abuse or misuse. Recently-developed products include pills that are formulated to lose their potency if they are crushed or dissolved.
