BUPRENEX
Clinical safety rating: caution
Comprehensive clinical and safety monograph for BUPRENEX (BUPRENEX).
Partial agonist at mu-opioid receptors; weak antagonist at kappa-opioid receptors.
| Metabolism | Primarily N-dealkylation via CYP3A4; also conjugation by UGT enzymes (UGT1A1, UGT2B7). |
| Excretion | Buprenorphine is primarily eliminated via fecal excretion (70%) as unchanged drug and metabolites, with renal excretion accounting for approximately 10-30% of the dose. |
| Half-life | Terminal elimination half-life is 37 hours (range 20-70 hours) due to slow dissociation from mu-opioid receptors, contributing to prolonged clinical effects. |
| Protein binding | 96% bound to alpha- and beta-globulins, and albumin. |
| Volume of Distribution | Volume of distribution is 430-600 L (approximately 2.8 L/kg), indicating extensive tissue distribution. |
| Bioavailability | Sublingual: 30-50% (due to first-pass metabolism); buccal: 50-60%; oral: 15-30% (not clinically used); intravenous: 100%. |
| Onset of Action | Sublingual: 15-30 minutes; intravenous: 2-5 minutes; intramuscular: 10-15 minutes. |
| Duration of Action | Analgesic duration: 4-8 hours (IV/IM) but up to 24 hours with sublingual administration due to high receptor affinity; duration is dose-dependent. |
0.3 mg intramuscularly or intravenously every 6 hours as needed for pain; may repeat once after 30-60 minutes if needed.
| Dosage form | INJECTABLE |
| Renal impairment | No specific dose adjustment required for GFR >30 mL/min; for GFR 15-30 mL/min, consider cautious dosing and extended intervals; for GFR <15 mL/min, use with caution and consider dose reduction. |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 50% and monitor; Child-Pugh C: avoid use or reduce dose by 75%. |
| Pediatric use | Not recommended for children under 2 years; for age 2-12 years: 2-6 mcg/kg intramuscularly or intravenously every 4-6 hours; maximum single dose 0.3 mg. |
| Geriatric use | Start with 0.15 mg intramuscularly or intravenously every 6 hours; titrate cautiously due to increased sensitivity and risk of respiratory depression. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for BUPRENEX (BUPRENEX).
| Breastfeeding | Buprenorphine is excreted into breast milk in low concentrations. The milk-to-plasma ratio (M/P) is approximately 0.5-0.9. Limited data suggest no adverse effects in breastfed infants at maternal doses up to 24 mg/day. However, monitor infant for sedation and respiratory depression. Benefits of breastfeeding outweigh risks in opioid-dependent mothers on maintenance therapy. |
| Teratogenic Risk | Buprenorphine (Buprenex) is classified as Pregnancy Category C. First trimester: Limited human data; animal studies show increased fetal loss and skeletal abnormalities at high doses. Second and third trimesters: Chronic use may lead to neonatal abstinence syndrome (NAS) and neonatal respiratory depression. Risk of preterm labor and low birth weight. Use only if benefit outweighs risk. |
■ FDA Black Box Warning
Risk of respiratory depression, particularly in non-opioid-tolerant patients; risk of neonatal opioid withdrawal syndrome with prolonged use during pregnancy; risk of death with intravenous administration; risk of serious adverse events when used with benzodiazepines or other CNS depressants.
| Serious Effects |
Hypersensitivity to buprenorphine; significant respiratory depression; acute or severe asthma; GI obstruction; elevated CSF pressure; use of MAOIs within 14 days.
| Precautions | Respiratory depression; CNS depression; risk of dependence and abuse; adrenal insufficiency; QT prolongation; severe injection site reactions; risk of precipitating withdrawal in opioid-dependent patients; neonatal withdrawal syndrome; impairment of ability to drive or operate machinery. |
| Food/Dietary | No specific food interactions are reported. Grapefruit juice has not been shown to significantly alter buprenorphine metabolism. Advise patients to maintain a balanced diet to manage opioid-induced constipation. |
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| Fetal Monitoring | Maternal: Assess vital signs, respiratory rate, level of sedation, and signs of opioid withdrawal or overdose. Fetal: Monitor fetal heart rate and uterine activity if used during labor. Neonatal: Observe for NAS (e.g., irritability, poor feeding, tremors) for at least 48 hours after delivery. Consider toxicology screen if indicated. |
| Fertility Effects | Buprenorphine may disrupt menstrual cycle due to hyperprolactinemia and hypothalamic-pituitary-gonadal axis suppression. In males, can cause decreased libido, erectile dysfunction, and reduced sperm count. These effects are generally reversible upon dose reduction or discontinuation. |
| Clinical Pearls | Buprenorphine (Buprenex) is a partial mu-opioid agonist with a ceiling effect on respiratory depression, making it safer than full agonists in overdose. It has high affinity for mu-receptors, which can precipitate withdrawal if given to opioid-dependent patients. Monitor for respiratory depression, especially in combination with CNS depressants. Use with caution in hepatic impairment; adjust dose in moderate to severe impairment. |
| Patient Advice | Do not stop taking this medication abruptly as it may cause withdrawal symptoms; follow your doctor's instructions for tapering. · Avoid alcohol and other CNS depressants (e.g., benzodiazepines, sedatives) as they can increase the risk of severe drowsiness or respiratory depression. · This medication can cause constipation; increase fluid and fiber intake, and consider stool softeners. · Store securely away from children and pets, as accidental ingestion can be fatal. · Do not drive or operate heavy machinery until you know how this medication affects you, as it may cause dizziness or drowsiness. |