PROBUPHINE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for PROBUPHINE (PROBUPHINE).
Partial mu-opioid receptor agonist and weak kappa-opioid receptor antagonist. Also inhibits norepinephrine and dopamine reuptake.
| Metabolism | Primarily metabolized by CYP3A4 and CYP2B6 to norbuprenorphine (active). Glucuronidation via UGT1A1 and UGT2B7. |
| Excretion | Primarily renal (70-80% as unchanged drug and active metabolite norbuprenorphine), biliary/fecal (20-30%) |
| Half-life | Terminal elimination half-life: 37 hours (range 24-48 h) due to slow release from tissue binding and enterohepatic recirculation; contributes to prolonged dosing interval (every 4 weeks) and delayed withdrawal onset. |
| Protein binding | 96% bound to plasma proteins (primarily alpha- and beta-globulins, minor albumin binding) |
| Volume of Distribution | Vd: 2.5-3.0 L/kg; large distribution due to high lipophilicity and extensive tissue binding, indicating slow redistribution. |
| Bioavailability | Sublingual: 30-50% (due to first-pass metabolism). Transdermal: 15-20% (rate-controlled delivery). Oral: <10% (extensive first-pass) and not clinically used. |
| Onset of Action | Sublingual: 30-60 minutes; peak effect at 1-2 hours. Transdermal: 12-24 hours; steady-state achieved by day 3. |
| Duration of Action | Sublingual: 6-8 hours for analgesic effect; maintenance effect on opioid cravings/withdrawal: 24-48 hours. Transdermal: 7 days with wear period; sustained release for 4 weeks with implant. |
Sublingual: 8 mg to 24 mg once daily initially, then 12-16 mg once daily; maximum 24 mg/day.
| Dosage form | IMPLANT |
| Renal impairment | No dose adjustment required for mild to moderate renal impairment. For severe (CrCl <30 mL/min): not recommended. |
| Liver impairment | Child-Pugh A: no adjustment. Child-Pugh B: reduce dose by 50%. Child-Pugh C: avoid use. |
| Pediatric use | Weight-based: 0.1-0.2 mg/kg sublingually once daily, titrate up to maximum 0.4 mg/kg/day; maximum 24 mg/day. |
| Geriatric use | Start at lower end of dosing range (e.g., 4-8 mg sublingually once daily) with cautious titration due to increased sensitivity and risk of CNS depression. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for PROBUPHINE (PROBUPHINE).
| Breastfeeding | Probupine is excreted into breast milk. M/P ratio is approximately 0.45. Infant daily dose is estimated at 1-5% of maternal weight-adjusted dose. Reports of sedation and poor suckling in breastfed infants; cautious use recommended, especially in neonates with UDP-glucuronosyltransferase deficiency. |
| Teratogenic Risk | Probupine is classified as FDA Pregnancy Category C. In animal studies, it caused fetal harm (increased resorption, skeletal anomalies) at doses 0.5 times the human dose. There are no adequate human studies. First trimester exposure may be associated with neural tube defects; second and third trimester exposure may cause fetal hydantoin syndrome (craniofacial anomalies, growth retardation, neurodevelopmental delay) and increased risk of hemorrhage due to vitamin K depletion. |
■ FDA Black Box Warning
Risk of respiratory depression, especially with concurrent use of CNS depressants or in patients with compromised respiratory function. Risk of neonatal opioid withdrawal syndrome with prolonged use during pregnancy. Potential for life-threatening QT prolongation at high doses.
| Serious Effects |
Hypersensitivity to buprenorphine; severe respiratory depression; acute or severe bronchial asthma; paralytic ileus; use of monoamine oxidase inhibitors within 14 days.
| Precautions | Severe respiratory depression; misuse and abuse potential; neonatal opioid withdrawal syndrome; adrenal insufficiency; hepatotoxicity; QT prolongation; dental decay with sublingual use; opioid withdrawal syndrome with naloxone coadministration. |
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| Fetal Monitoring | Monitor maternal serum probupine trough levels (target 10-20 mcg/mL). Assess CBC with differential, liver function tests, coagulation profile (PT/INR) monthly. Fetal surveillance includes ultrasonography for growth and anatomy at 18-20 weeks; nonstress test and biophysical profile in third trimester. Monitor for neonatal withdrawal syndrome after delivery. |
| Fertility Effects | In males, probupine may cause decreased sperm count and motility, and reversible azoospermia. In females, it may cause menstrual irregularities and anovulation. Folate supplementation (5 mg/day) is recommended prior to conception due to antifolate effects. |