BUPRENORPHINE HYDROCHLORIDE AND NALOXONE HYDROCHLORIDE
Clinical safety rating: safe
No significant drug interactions Can precipitate acute withdrawal in patients dependent on opioids.
Buprenorphine is a partial mu-opioid receptor agonist and a weak kappa-opioid receptor antagonist; naloxone is a mu-opioid receptor antagonist that is added to deter intravenous abuse.
| Metabolism | Buprenorphine is primarily metabolized by CYP3A4 to norbuprenorphine; naloxone is metabolized by UDP-glucuronosyltransferases (UGT1A1, UGT1A3). |
| Excretion | Buprenorphine: ~70% fecal via biliary excretion, ~30% renal as unchanged drug and metabolites. Naloxone: primarily hepatic metabolism, ~50% renal excretion of metabolites within 6h. |
| Half-life | Buprenorphine: terminal half-life 24-60 hours (mean ~37h) due to slow dissociation from mu-opioid receptors; naloxone: ~2-12 hours (mean ~1-2h IV, slightly longer sublingual). |
| Protein binding | Buprenorphine: ~96% bound to alpha- and beta-globulins; naloxone: ~45% bound to albumin (primarily). |
| Volume of Distribution | Buprenorphine: Vd ~2.5-4.0 L/kg (large distribution due to lipophilicity); naloxone: Vd ~2.0 L/kg. |
| Bioavailability | Sublingual buprenorphine: ~30-50% (avoid first-pass); sublingual naloxone: ~10% (low); IV: 100% both. |
| Onset of Action | Sublingual: buprenorphine onset 15-30 min, naloxone minimal sublingual absorption; IV: buprenorphine onset 2-5 min, naloxone 1-2 min. |
| Duration of Action | Sublingual: buprenorphine duration 18-24h (long due to high receptor affinity); naloxone: 30-60 min (sublingual negligible effect). |
| Molecular Weight | Buprenorphine HCl: 504.09 Da; Naloxone HCl: 363.84 Da; combination product: weighted average not applicable. |
Sublingual tablet: initially 2/0.5 mg buprenorphine/naloxone, titrated to maintenance 4/1 mg to 24/6 mg once daily; administered sublingually as a single daily dose.
| Dosage form | TABLET |
| Renal impairment | For GFR <30 mL/min: use with caution, dose reduction may be necessary; avoid in severe impairment (creatinine clearance <15 mL/min) due to naloxone accumulation. |
| Liver impairment | Child-Pugh Class A: no adjustment. Child-Pugh Class B: reduce starting dose by 50%, monitor for oversedation. Child-Pugh Class C: not recommended. |
| Pediatric use | Not approved for pediatric patients under 16 years for opioid use disorder; safety and efficacy not established. |
| Geriatric use | Initiate at lower end of dosing range (e.g., 2/0.5 mg sublingually once daily) due to increased sensitivity and potential for hepatic/renal impairment; titrate slowly and monitor for CNS depression. |
| 1st trimester | No adequate studies in pregnant women; use only if potential benefit justifies risk to fetus. Neonatal withdrawal syndrome possible. |
| 2nd trimester | Same as t1; opioid dependence treatment may be continued under careful medical supervision. |
| 3rd trimester | Risk of neonatal opioid withdrawal syndrome; use only if maternal benefit outweighs fetal risk. May cause respiratory depression in neonate if used near term. |
Clinical note
No significant drug interactions Can precipitate acute withdrawal in patients dependent on opioids.
| FDA category | Animal |
| Placental transfer | Buprenorphine crosses the placenta; cord blood concentrations are approximately 50-100% of maternal plasma concentrations. Naloxone also crosses but less extensively. |
■ FDA Black Box Warning
Risk of respiratory depression, particularly in patients using other CNS depressants, and risk of neonatal opioid withdrawal syndrome with prolonged use during pregnancy.
| Common Effects | Precipitated withdrawal |
| Serious Effects |
Hypersensitivity to buprenorphine or naloxoneSignificant respiratory depressionAcute or severe bronchial asthmaKnown or suspected gastrointestinal obstructionPatients with severe hepatic impairment
| Precautions | Respiratory depression risk with intravenous administration, Hepatotoxicity (elevated liver enzymes, hepatic failure), Adrenal insufficiency with chronic use, Interaction with benzodiazepines and other CNS depressants, Precipitation of withdrawal in opioid-dependent patients if administered too soon after last opioid use, Dependence and abuse potential (Schedule III controlled substance), Neonatal opioid withdrawal syndrome if used during pregnancy |
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| Breastfeeding |
| Buprenorphine is excreted in breast milk in low concentrations; naloxone has poor oral bioavailability. Risk of infant sedation and respiratory depression is low at maternal doses used for maintenance therapy. Monitor infant for drowsiness and feeding difficulties. |
| Lactation Rating | L3 (Moderately Safe) or 'Moderately Safe' |
| Teratogenic Risk | Pregnancy category C: First trimester: Limited data; no clear evidence of major malformations, but opioid exposure may be associated with neural tube defects in some studies. Second and third trimesters: Risk of neonatal opioid withdrawal syndrome (NOWS) with chronic use. No known specific teratogenicity; however, maternal opioid use may lead to fetal growth restriction, preterm birth, and stillbirth. Buprenorphine/naloxone is preferred over methadone in pregnancy due to less neonatal respiratory depression and NOWS severity. |
| Fetal Monitoring | Maternal: Baseline liver function tests (LFTs) prior to initiation and periodically; ECG if QT prolongation risk; urine drug screens throughout pregnancy; adherence monitoring. Fetal: Ultrasound for growth restriction, amniotic fluid index, and anatomy; fetal non-stress testing or biophysical profile in third trimester if high risk. Neonatal: Observe for signs of NOWS (e.g., irritability, feeding difficulties, tremors) for at least 72 hours after birth; use validated scoring tools (e.g., Finnegan scale). |
| Fertility Effects | Opioids may cause menstrual irregularities (e.g., amenorrhea, anovulation) due to hypothalamic-pituitary-gonadal axis suppression, which may be reversible upon discontinuation or stabilization. No definitive evidence of permanent infertility. Men may experience decreased libido and erectile dysfunction. Buprenorphine/naloxone may improve fertility outcomes compared to illicit opioid use by stabilizing cycles. Advise women of reproductive age about contraceptive options if not planning pregnancy. |
| Food/Dietary |
| No significant food interactions; grapefruit juice may increase buprenorphine levels but not considered clinically relevant; alcohol is contraindicated due to additive CNS depression; take on an empty stomach or with food if GI upset occurs. |
| Clinical Pearls | Avoid in patients with known respiratory insufficiency or acute opioid intoxication; use with caution in hepatic impairment; buprenorphine has a ceiling effect for respiratory depression; naloxone component prevents IV abuse; monitor for precipitated withdrawal if initiated too soon after last opioid use; requires at least 12 hours since last short-acting opioid or 24-72 hours for long-acting opioids; can cause QT prolongation at high doses; sublingual absorption is critical; consider dose adjustment in renal impairment. |
| Patient Advice | Place the tablet/film under the tongue until fully dissolved; do not chew, swallow, or crush. · Do not use alcohol or other sedatives (benzodiazepines, muscle relaxants, sleeping pills) as this can cause severe respiratory depression or coma. · Keep out of reach of children and pets; accidental ingestion is life-threatening. · Avoid driving or operating machinery until you know how the medication affects you. · Do not stop suddenly; withdrawal symptoms can occur; taper under medical supervision. · Store at room temperature away from moisture and heat. · Tell all healthcare providers you are taking this medication before any surgery or new prescriptions. · Seek emergency help if you experience difficulty breathing, chest pain, or signs of allergic reaction (rash, swelling). · If you miss a dose, skip it; do not double dose. |