PROPHENE 65
Clinical safety rating: caution
Comprehensive clinical and safety monograph for PROPHENE 65 (PROPHENE 65).
Propoxyphene is a weak opioid agonist that binds to mu-opioid receptors in the CNS, inhibiting ascending pain pathways and altering perception of pain. It also has local anesthetic and moderate antitussive effects.
| Metabolism | Hepatic via CYP3A4 and CYP2D6 to norpropoxyphene (active metabolite with longer half-life). Minor metabolism via N-demethylation and glucuronidation. |
| Excretion | Renal elimination of unchanged drug and metabolites: propoxyphene and its major metabolite norpropoxyphene account for ~20-30% as unchanged drug in urine; remainder as conjugated metabolites. Biliary/fecal elimination accounts for <10%. |
| Half-life | Terminal elimination half-life of propoxyphene: 6-12 hours (mean ~8 hours); norpropoxyphene half-life: 22-36 hours, leading to accumulation with chronic dosing. Clinical context: prolonged half-life in elderly and hepatic impairment increases risk of toxicity. |
| Protein binding | Propoxyphene: ~78% bound to albumin; norpropoxyphene: ~95% bound to albumin. |
| Volume of Distribution | Volume of distribution: 16-20 L/kg (suggesting extensive tissue binding). Clinical meaning: high Vd indicates wide distribution into tissues, contributing to long half-life and potential for accumulation. |
| Bioavailability | Oral: approximately 30-70% (first-pass metabolism). Other routes: not formulated for parenteral use. |
| Onset of Action | Oral: 30-60 minutes; peak effect at 2-2.5 hours. Not suitable for intravenous use. |
| Duration of Action | Analgesic effect lasts 4-6 hours after oral administration. Clinical notes: norpropoxyphene accumulation may prolong effects but also increase toxicity risk. |
Propoxyphene napsylate 100 mg orally every 4 hours as needed for pain; maximum 600 mg/day.
| Dosage form | CAPSULE |
| Renal impairment | CrCl < 30 mL/min: Avoid use due to accumulation of toxic metabolite norpropoxyphene. CrCl 30-50 mL/min: Reduce dose to 50 mg every 6 hours. |
| Liver impairment | Child-Pugh Class C: Contraindicated. Child-Pugh Class B: Avoid use or reduce dose by 50% with close monitoring. |
| Pediatric use | Not recommended for use in pediatric patients due to risk of respiratory depression and lack of established safety. |
| Geriatric use | Initiate at lowest dose (e.g., 50 mg every 6 hours) and titrate cautiously; avoid in patients with renal impairment or concomitant CNS depressants. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for PROPHENE 65 (PROPHENE 65).
| Breastfeeding | Excreted into breast milk in small amounts; M/P ratio approximately 0.7. Clinical studies show no adverse effects in infants at therapeutic maternal doses. However, due to potential for prostaglandin inhibition, caution is advised, especially in premature infants or those with platelet dysfunction. Consider monitoring infant for bruising, bleeding, or gastrointestinal effects. |
| Teratogenic Risk | FDA Pregnancy Category C. First trimester: Risk of neural tube defects, cardiovascular malformations, and cleft lip/palate based on prostaglandin synthesis inhibition. Second trimester: Limited data; potential for oligohydramnios. Third trimester: Premature closure of ductus arteriosus, fetal renal dysfunction with oligohydramnios, and neonatal pulmonary hypertension. Avoid in third trimester unless compelling need. |
■ FDA Black Box Warning
WARNING: RISK OF CARDIAC TOXICITY AND OVERDOSE. Propoxyphene has been withdrawn from the US market due to risk of fatal cardiac arrhythmias (QT prolongation, torsade de pointes) even at therapeutic doses. Use with alcohol or other CNS depressants increases risk of respiratory depression and death.
| Serious Effects |
Hypersensitivity to propoxyphene or opioid cross-sensitivity; known QT prolongation; concurrent use of MAO inhibitors; severe asthma or respiratory depression; obstructive airway disease; paralytic ileus; pregnancy and breastfeeding.
| Precautions | Cardiac toxicity (QT prolongation, torsade de pointes); respiratory depression; CNS depression (additive with alcohol/other depressants); risk of abuse and dependence; renal or hepatic impairment; elderly patients; history of head injury; increased intracranial pressure; seizure disorders; acute abdominal conditions. |
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| Fetal Monitoring | Maternal: Platelet count, bleeding time, liver function tests, renal function, blood pressure monitoring due to increased risk of gestational hypertension and preeclampsia. Fetal: Ultrasound for amniotic fluid volume (oligohydramnios), ductus arteriosus patency via Doppler echocardiography in third trimester. Non-stress test or biophysical profile if prolonged use. |
| Fertility Effects | Reversible inhibition of ovulation due to prostaglandin synthesis inhibition. May delay conception in women attempting pregnancy. In males, no significant impact on spermatogenesis or fertility reported. |