First approved by the FDA in 1957, propoxyphene is an opioid used to relieve mild to moderate pain. The terms “Darvon” and “Darvocet” are two of the primary trade names through which propoxyphene is sold. “Darvon” denotes the use of propoxyphene in its singular form while “Darvocet” is a combination of propoxyphene and acetaminophen, its combination form.
Due to its linkages to abnormal heart electrical activity, abnormal heart rhythm ,ventricular fibrillation (heart attack), and brain damage due to lack of oxygen, propoxyphene was withdrawn by the European Medicines Agency (EMEA) in January of 2009 and, in June of 2009, the FDA issued a black box warning for propoxyphene, alerting patients and health care professionals to the risk of a fatal overdose. As of 2010, over 10 million Americans have been prescribed propoxyphene in some form.
< As of November of 2010, propoxyphene has been shown to cause significant increases in the electrical activity of the heart, which has been shown to be linked to respiratory failure, circulatory failure, brain damage, and heart attack (sometimes leading to death). When compared with other opioids (drugs used to relieve pain), propoxyphene drugs have been shown to be twice as fatal, with 92% of deaths linked to using propoxyphene in combination with other drugs and alcohol. There has been a proven link between propoxyphene’s effect on heart electrical activity and increased risk of heart attack.
Additionally, its link to respiratory problems may cause temporary oxygen starvation to the brain, which may lead to permanent brain damage. Propoxyphene has also been shown to be more dangerous for patients with impaired kidneys. Notably, the ill effects of propoxyphene have not been shown to be cumulative.
In July 2009, the FDA decided to permit continued marketing of propoxyphene with a new boxed warning added to the drug label alerting patients and health care professionals to the risk of a fatal overdose. Meanwhile, Xanodyne, the producer of Darvon and Darvocet, conducted a study in healthy volunteers to determine an appropriate dose that could be used in the definitive cardiac study. Data from that study demonstrated that even when propoxyphene was taken at recommended doses, there were significant changes to the electrical activity of the heart including prolonged PR interval( linked to heart blockages, heart attack, and myocarditis), widened QRS complex( linked to sudden death, ventricular fibrillation) and prolonged QT interval( linked to sudden death, heart attack, and heart failure).
In light of these new scientific findings, FDA determined the post-marketing safety signals for this drug have taken on new importance, and the overall balance of risk and benefit can no longer be considered favorable. The agency is recommending that propoxyphene products be removed from the US market.
Propoxyphene has been most directly connected to negatively impacting the electrical activity of the heart. This interference has been linked to a number of heart problems including heart arrhythmia, heart attack, increased heart electrical activity (EKG), prolonged heart QT and PR intervals, widening of the heart’s QRS complex, and high heart toxicity. In addition, Darvon and Darvocet have been linked to respiratory problems, circulatory problems, sudden death and the potential need for a pacemaker.