Propoxyphene Safety and Efficacy in Question

            The safety and efficacy of propoxyphene products has recently been called into question by the FDA.  Propoxyphene is a weak opioid agonist indicated for the treatment of mild to moderate pain.  However, its side effects and potential for abuse may outweigh its benefits as an analgesic.  In the UK, propoxyphene was pulled off the market due its use in suicides and limited efficacy.  

            Efficacy studies have shown various propoxyphene products to be equal or inferior to ibuprofen, acetaminophen, diclofenac and aspirin when used for conditions such as osteoarthritis, postoperative pain and episiotomy pain.  Propoxyphene was involved in 5.6% of U.S. overdose deaths between the years of 1981 and 1999.  During the same period, 2,110 accidental deaths were reported involving propoxyphene.  Of all propoxyphene deaths, 38.6% were classified as accidental and could possibly have been avoided.  Overdoses of propoxyphene can cause cardiac toxicity due to the negative chronotropic and inotropic effects of propoxyphene and its metabolite.  Lethal doses may be as low as 9mg/kg with a possible mortality rate of 30%. 

            With this in mind, propoxyphene should be prescribed sparingly and never used for chronic pain.  Acetaminophen or an NSAID can be prescribed in its place and may be just as effective.  Other options also include tramadol or an acetaminophen/opioid combination.  If propoxyphene is used, it should be avoided in patients at risk of suicide and increased dosing intervals (i.e. every six hours) are suggested for elderly patients.  Until the FDA makes its final ruling, cautious use of propoxyphene is recommended.

1.  Propoxyphene: safety and efficacy. Pharmacist's Letter/Prescriber's Letter 2009;25(3):250301.
2. www.mdconsult.com
3. www.ashp.org

Prepared by Michael A. Biddle, Jr., Doctor of Pharmacy Candidate