The Darvon and Darvocet recall announced last month due to the drugs’ association with serious and sometimes fatal heart rhythm problems was about 30 years too late. For at least that long, patient advocates had raised questions about the safety of Darvon, Darvocet and other propoxyphene medications, but had no luck convincing the Food & Drug Administration (FDA) to pull the dangerous painkillers from the market.
Propoxyphene is an opiod painkiller that was already known to be highly addictive. In November, the FDA announced that Xanodyne Pharmaceuticals Inc. had agreed to pull the medications after a study linked them to serious and possibly fatal heart rhythm problems. The agency said it was also asking the manufacturers of generic propoxyphene-containing products to remove those products from the market.
Since 1978, the consumer group Public Citizen has petitioned the FDA twice to initiate Darvocet and Darvon recall propoxyphene products like Darvon and Darvocet from the market (as well as other propoxyphene products). According to the group, evidence going back more than 30 years indicates that propoxyphene is not very effective, is toxic at doses not much higher than the recommended dose because a heart-toxic metabolite accumulates in the body, and is somewhat addictive. Public Citizen asserts that it has been linked to many thousands of US deaths since 1981, a large proportion of which were likely caused by cardiac toxicity, including the interruption of electrical conduction in the heart.
As Public Citizen points out, propoxyphene bans were announced in the United Kingdom almost six years ago, and in Europe, almost 1½ years ago. In announcing the ban in 2005, regulators in the United Kingdom stated that the efficacy of propoxyphene “is poorly established and the risk of toxicity in overdose, both accidental and deliberate, is unacceptable†and that “n relation to safety, there is evidence that fatal toxicity may occur with a small multiple of the normal therapeutic dose and a proportion of fatalities are caused by inadvertent overdose.â€
In January 2009, an FDA advisory panel narrowly voted 14-12 to recommend that the FDA remove Darvon and similar products from the market.
Rather than heed the advice of its advisory panel, the FDA decided to permit continued marketing of Darvon, Darvocet and other propoxyphene products, but required that a new boxed warning be added to the drug label alerting patients and health care professionals to the risk of a fatal overdose. While the new warning did not include mention of heart rhythm problems, the agency required Xanodyne Pharmaceuticals, the company that markets Darvon and Darvocet, to conduct a new safety study assessing what it said were unanswered questions about the effects of propoxyphene on the heart. The results of that study finally prompted the FDA to request the medications be removed from the market.
According to Public Citizen, the FDA’s failure to take action sooner may have come at a high cost to patients taking drugs like Darvon and Darvocet. Since the United Kingdom ban was announced in 2005, approximately 120 million retail prescriptions have been filled in the US for propoxyphene-containing drugs. Public Citizen claims that due to FDA negligence, at least 1,000 to 2,000 or more people in the US have died from using propoxyphene during that time frame.
The FDA waited to ban propoxyphene because it claimed it needed to order a human study to find that “the drug puts patients at risk of potentially serious or even fatal heart rhythm abnormalities.” But as Pubic Citizen points out, a study on dogs published 31 years ago, researchers at Eli Lilly, the discoverer of propoxyphene, stated that “cardiac conduction depression may be a factor in some of the cardiac toxicities associated with propoxyphene overdose.†This study examined the same kind of function measured in the human study now being put forth by the FDA as a justification for belatedly banning propoxyphene, Public Citizen said.
On the heels of the propoxyphene recall, Public Citizen is now calling for a congressional investigation of the FDA’s handling of the drug.
