PROPHENE 65
Clinical safety rating
cautionComprehensive 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. |
| Molecular Weight | 325.4 |
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 | Avoid use; risk of premature closure of ductus arteriosus and oligohydramnios. NSAIDs in first trimester may increase risk of miscarriage and congenital defects. |
| 2nd trimester | Use only if clearly needed; avoid prolonged use due to risk of premature closure of ductus arteriosus and oligohydramnios. |
| 3rd trimester | Contraindicated from 30 weeks gestation onwards due to risk of premature closure of ductus arteriosus, oligohydramnios, and neonatal renal impairment. |
Clinical note
Comprehensive clinical and safety monograph for PROPHENE 65 (PROPHENE 65).
| Placental transfer | Crosses placenta; detected in fetal plasma at approximately 50% of maternal concentration. |
| Breastfeeding | Excreted into breast milk in low amounts; not expected to cause adverse effects in infants. However, consider potential for infant sensitivity and avoid in nursing mothers with premature infants or those with renal impairment. |
| Lactation Rating | L2 (Probably Compatible) |
| 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. |
| 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. |
■ 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 |
History of hypersensitivity to propoxyphene or any ingredient in the formulationAcute or severe bronchial asthma in patients with known hypersensitivityGI obstruction (e.g., paralytic ileus, known or suspected obstruction)Concurrent use with MAOIs or within 14 days of discontinuation
| 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. |
| Food/Dietary | No specific food interactions; avoid excessive grapefruit juice as it may increase propoxyphene levels. |
| Clinical Pearls | Propoxyphene is a weak opioid analgesic; avoid in patients with suicidal ideation or history of substance abuse due to risk of overdose and cardiac toxicity (QT prolongation). Use with caution in elderly and renal impairment; start at lower doses. Monitor for respiratory depression, especially when combined with CNS depressants. |
| Patient Advice | Take exactly as prescribed; do not increase dose or frequency. · Do not consume alcohol or other CNS depressants. · May cause dizziness or drowsiness; avoid driving until known effect. · Report any signs of allergic reaction or irregular heartbeat. · Do not stop abruptly; withdrawal symptoms may occur. |
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