Propoxyphene Morphine Equivalent Dose
Propoxyphene should not be used for pain management and has no established reliable morphine equivalent dose for clinical practice. 1
Strong Recommendation Against Use
Propoxyphene is explicitly contraindicated for chronic pain management and is not recommended for cancer patients. 1 The National Comprehensive Cancer Network guidelines specifically state that propoxyphene, along with meperidine, should be avoided because accumulation of renally cleared metabolites (norpropoxyphene) may result in neurotoxicity or cardiac arrhythmias, particularly in patients with impaired renal function or dehydration. 1
Why No Conversion Exists
Propoxyphene is excluded from opioid conversion protocols. Studies examining opioid-induced constipation specifically exclude propoxyphene when defining stable opioid use, noting that full opioid agonists "other than meperidine and propoxyphene" should be used when calculating morphine equivalents. 1
The drug lacks efficacy comparable to morphine. Research demonstrates that propoxyphene is no more effective than acetaminophen alone, yet causes opioid side effects including respiratory depression, cardiotoxicity, and seizures. 2, 3, 4
Norpropoxyphene, the active metabolite, is non-opioid and cardiotoxic. This metabolite causes QTc prolongation and arrhythmias independent of any analgesic effect, making standard opioid conversion calculations inappropriate and dangerous. 4
Additional Safety Concerns
Drug interaction risk with tamoxifen. Propoxyphene inhibits CYP2D6, which may increase breast cancer recurrence risk in patients treated with tamoxifen, providing another reason to avoid this agent entirely. 1
High mortality risk. The drug has been involved in numerous drug-related deaths, with toxicity far outweighing any therapeutic benefit. 2, 4
Clinical Alternative
If a patient is currently on propoxyphene, switch directly to acetaminophen or another appropriate analgesic rather than attempting opioid conversion. 2, 3 For pain requiring opioid therapy, morphine at initial doses of 5-15 mg orally (or 2-5 mg IV) for opioid-naive patients is the preferred starting approach. 1