The Food and Drug Administration has requested that manufacturers involved in the production of medications that contain propoxyphene voluntarily recall these products off the U.S. market. Xanodyne, the manufacturer of DARVON TM and DARVOCET TM, has already complied with the recall request from the FDA. Generic manufacturers of products that contain propoxyphene are also expected to comply with the recall following the availability of new safety information.
Propoxyphene Capsules for Pain
Propoxyphene hydrochloride (DARVON TM) acts centrally as an opiate-based analgesic that is commonly used to treat pain. Inside the body, propoxyphene is further metabolized into norpropoxyphene and both compounds are capable of blocking sodium channels resulting in the inhibition of pain signals. Propoxyphene is extensively metabolized in the liver by CYP3A4 enzymes. Since the same enzymes also metabolize many other drugs, drug interactions can result in higher propoxyphene levels found inside the body. As with other opiate medications, propoxyphene can cause respiratory depression, central nervous system depression, hypotension and issues with dependency.
In some cases, propoxyphene hydrochloride is combined with acetaminophen (DARVOCET TM), for a combined analgesic effect. Xanodyne is also the manufacturer of Darvocet A500 TM, a similar product to Darvocet TM, but contains a larger amount of acetaminophen.
Darvon-N TM and Darvocet-N TM
Propoxyphene has also been produced as a napsylate salt denoted by the letter “N” after the brand name. In contrast to the propoxyphene hydrochloride formulation, propoxyphene napsylate has greater stability, allowing for the production of a tablet dosage form. Since propoxyphene napsylate is a heavier compound, a greater amount by milligram weight is required to have the same potency as propoxyphene hydrochloride.
Propoxyphene Products Recalled
In November 2010, the FDA requested a recall of all products containing propoxyphene. In previous discussions and reviews of propoxyphene, the FDA had decided to keep the drug on the market, with the stipulation that additional warnings be included in labeling and further studies be conducted on the effects of propoxyphene on the heart. Although propoxyphene blocks sodium channels for pain inhibition, the drug also has the potential to block conduction channels in the heart, which can lead to arrhythmias and other conduction abnormalities. Unfortunately, additional safety data and further studies requested by the FDA did show that propoxyphene could result in altered electrical activity in the heart, possibly resulting in sudden death.
As a result, the Food and Drug Administration has decided that the risks outweigh the potential benefits and has advised physicians to stop prescribing propoxyphene. In addition, pharmacies should no longer dispense the medications, and patients currently taking propoxyphene should contact their physician regarding other drug options for pain control.
Disclaimer: The information contained in this article is for educational purposes only and should not be used for diagnosis or to guide treatment without the opinion of a health professional. Any reader who is concerned about his or her health should contact a doctor for advice.
References:
The Food and Drug Administration: “News Release: Xanodyne Agrees to Withdraw Propoxphene from the U.S. Market” (Accessed November 22, 2010).
Xanodyne Pharmaceuticals: “Product Package Inserts” (Accessed November 22, 2010).
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