The announcement by the U.S.Food and Drug Administration (FDA) 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 UK almost six years ago, and in Europe, almost 1½ 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. In announcing the ban in 2005, the UK stated that the efficacy of propoxyphene (sold generically and under the brand name Darvon) “is poorly established and the risk of toxicity in overdose, both accidental and deliberate, is unacceptable” and that “[I]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.” The FDA’s claim that this is the first evidence that the drug is dangerous at the “standard therapeutic dose” thus rings dangerously hollow.
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.
Evidence going back more than 30 years indicates that propoxyphene is not very effective, is toxic at doses not much higher than the recommend dose because a heart-toxic metabolite accumulates in the body, and is somewhat addictive. It has been linked to many thousands of U.S. deaths since 1981, a large proportion of which were likely caused by cardiac toxicity, including the interruption of electrical conduction in the heart.
Since the time of the UK announcement in January 2005 of a phased, two-year withdrawal of this drug (which was followed by an immediate steep decline in use), approximately 120 million retail prescriptions have been filled in the U.S. for propoxyphene-containing drugs. These include Darvocet, which contains propoxyphene and acetaminophen and, primarily, the generic versions of the drug.
Due to FDA negligence, at least 1,000 to 2,000 or more people in the U.S. have died from using propoxyphene since time the UK ban was announced. The best forensic data, the kind relied upon in those countries for the UK and European bans, come from Florida where, because of routine drug testing required by the state medical examiner as part of many autopsies, deaths are categorized as being “caused” by certain drugs if the levels found are to be above a certain level. From 2005 through 2009, in Florida alone, 395 deaths were “caused” by propoxyphene. If data from 2007 are representative, in that year, 78 percent of the Florida deaths caused by propoxyphene were ruled accidental.
Our February 2006 petition to the FDA to ban the drug, following the UK ban announcement, did not even result in an FDA advisory committee hearing until we had sued the agency in 2008 to force them to respond to our petition. The subsequent January 2009 FDA advisory committee hearing resulted in a 14-12 vote in favor of banning propoxyphene, despite some FDA efforts to sway the committee against voting for a ban. In July 2009, several weeks after the European Medicines Agency announced its ban, the FDA denied our petition to ban the drug.
The FDA’s pitiful excuse that 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” before deciding whether to ban propoxyphene only emphasizes how out-of-step the agency is with the rest of the world – which already had enough human evidence of death and near-death in tens of thousands of people to act accordingly.
In a study on dogs published 31 years ago, researchers at Lilly, the discoverer of propoxyphene, stated that “cardiac conduction depression may be a factor in some of the [human] 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.
We will ask for and support a congressional investigation into whom in the FDA, specifically in the Center for Drug Evaluation and Research, was responsible for the loss of so many lives in this country. It is clear that long before today, many drug safety experts in the Office of Surveillance and Epidemiology had decided the drug should be removed from the market.
Dr. Sidney Wolfe is the director of the Health Research Group at Public Citizen.
A chronology of events related to Darvon and Darvocet: