SUBUTEX

Clinical safety rating: caution

Comprehensive clinical and safety monograph for SUBUTEX (SUBUTEX).

How it works

Partial agonist at mu-opioid receptors; antagonist at kappa-opioid receptors. High affinity binding reduces withdrawal symptoms and blocks effects of full agonists.

What the body does with it

Metabolism	N-dealkylation by CYP3A4 (major pathway) to norbuprenorphine; also undergoes glucuronidation. CYP2C8 and CYP2C9 minor contributions.
Excretion	Renal: approximately 30% of administered dose excreted unchanged in urine. Fecal: about 70% eliminated via feces, predominantly as conjugated metabolites. Biliary excretion contributes to fecal elimination.
Half-life	Terminal elimination half-life of buprenorphine ranges from 24 to 60 hours (mean ~37 hours). Clinical context: Long half-life allows for alternate-day dosing in maintenance therapy but requires careful monitoring for accumulation in renal impairment.
Protein binding	Approximately 96% bound to plasma proteins, primarily alpha- and beta-globulins, with minimal binding to albumin.
Volume of Distribution	Volume of distribution is approximately 2.5 L/kg (range 1.0-4.0 L/kg). This large Vd indicates extensive tissue distribution, including into the brain and adipose tissue.
Bioavailability	Sublingual: 40-90% (mean 50-60%) due to first-pass metabolism; oral bioavailability is <10% due to extensive hepatic extraction.
Onset of Action	Sublingual: onset of analgesic effect within 15-30 minutes; peak effect at 1-2 hours. Sublingual administration for opioid dependence: onset of withdrawal suppression within 30-60 minutes.
Duration of Action	Analgesic effect: 6-8 hours due to high affinity and slow dissociation from mu-opioid receptors. For opioid dependence: suppression of withdrawal for 24-72 hours depending on dose and tolerance.

Classification & Brands

Dosing & administration

Sublingual tablet: initial 2-4 mg, titrated to 8-16 mg daily as a single dose; maximum 24 mg per day.

Dosage form	TABLET
Renal impairment	No dose adjustment required for mild to moderate renal impairment; caution in severe impairment (CrCl <30 mL/min) with extended dosing intervals.
Liver impairment	Child-Pugh Class A: no adjustment; Class B: reduce dose by 50%; Class C: avoid use or use with extreme caution at reduced doses.
Pediatric use	Not approved for patients <16 years; safety and efficacy not established.
Geriatric use	No specific dose adjustment recommended; monitor for increased sensitivity and adverse effects; consider lower starting doses and slower titration.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for SUBUTEX (SUBUTEX).

Breastfeeding	Buprenorphine is excreted into breast milk. Average infant dose is approximately 1-2% of maternal weight-adjusted dose. M/P ratio not well established. Monitor infant for sedation and respiratory depression; generally considered compatible with breastfeeding if mother is stable.
Teratogenic Risk	Buprenorphine is classified as Pregnancy Category C. First trimester: Limited human data; animal studies show increased risk of neural tube defects at high doses. Second and third trimesters: Chronic use may lead to neonatal abstinence syndrome (NAS). No increased risk of major malformations in human studies.

Warnings & precautions

■ FDA Black Box Warning

Risk of serious injury or death if administered intravenously; only prescribe for sublingual or buccal use. Risk of respiratory depression, especially in opioid-naive patients or if used with CNS depressants. Risk of neonatal opioid withdrawal syndrome with prolonged use during pregnancy. Concomitant use with benzodiazepines or other CNS depressants may cause severe respiratory depression, coma, and death.

Side Effect Profile

Serious Effects

Absolute Contraindications

Hypersensitivity to buprenorphine or naloxone; severe respiratory insufficiency; severe acute bronchial asthma; paralytic ileus; use in patients with known or suspected gastrointestinal obstruction.

Clinical Precautions

Precautions

Respiratory depression; risk of drug interactions with CNS depressants; impairment of cognitive/motor function; adrenal insufficiency; QT prolongation; hepatic impairment; neonatal withdrawal; misuse/abuse potential; abrupt discontinuation leads to withdrawal; individuals with compromised respiratory function; elevated CSF pressure; head injury.

Clinical Tips & Counseling

Drug interactions

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SUBUTEX

Clinical safety rating: caution

Comprehensive clinical and safety monograph for SUBUTEX (SUBUTEX).

How it works

Partial agonist at mu-opioid receptors; antagonist at kappa-opioid receptors. High affinity binding reduces withdrawal symptoms and blocks effects of full agonists.

What the body does with it

Metabolism	N-dealkylation by CYP3A4 (major pathway) to norbuprenorphine; also undergoes glucuronidation. CYP2C8 and CYP2C9 minor contributions.
Excretion	Renal: approximately 30% of administered dose excreted unchanged in urine. Fecal: about 70% eliminated via feces, predominantly as conjugated metabolites. Biliary excretion contributes to fecal elimination.
Half-life	Terminal elimination half-life of buprenorphine ranges from 24 to 60 hours (mean ~37 hours). Clinical context: Long half-life allows for alternate-day dosing in maintenance therapy but requires careful monitoring for accumulation in renal impairment.
Protein binding	Approximately 96% bound to plasma proteins, primarily alpha- and beta-globulins, with minimal binding to albumin.
Volume of Distribution	Volume of distribution is approximately 2.5 L/kg (range 1.0-4.0 L/kg). This large Vd indicates extensive tissue distribution, including into the brain and adipose tissue.
Bioavailability	Sublingual: 40-90% (mean 50-60%) due to first-pass metabolism; oral bioavailability is <10% due to extensive hepatic extraction.
Onset of Action	Sublingual: onset of analgesic effect within 15-30 minutes; peak effect at 1-2 hours. Sublingual administration for opioid dependence: onset of withdrawal suppression within 30-60 minutes.
Duration of Action	Analgesic effect: 6-8 hours due to high affinity and slow dissociation from mu-opioid receptors. For opioid dependence: suppression of withdrawal for 24-72 hours depending on dose and tolerance.

Classification & Brands

Dosing & administration

Sublingual tablet: initial 2-4 mg, titrated to 8-16 mg daily as a single dose; maximum 24 mg per day.

Dosage form	TABLET
Renal impairment	No dose adjustment required for mild to moderate renal impairment; caution in severe impairment (CrCl <30 mL/min) with extended dosing intervals.
Liver impairment	Child-Pugh Class A: no adjustment; Class B: reduce dose by 50%; Class C: avoid use or use with extreme caution at reduced doses.
Pediatric use	Not approved for patients <16 years; safety and efficacy not established.
Geriatric use	No specific dose adjustment recommended; monitor for increased sensitivity and adverse effects; consider lower starting doses and slower titration.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for SUBUTEX (SUBUTEX).

Breastfeeding	Buprenorphine is excreted into breast milk. Average infant dose is approximately 1-2% of maternal weight-adjusted dose. M/P ratio not well established. Monitor infant for sedation and respiratory depression; generally considered compatible with breastfeeding if mother is stable.
Teratogenic Risk	Buprenorphine is classified as Pregnancy Category C. First trimester: Limited human data; animal studies show increased risk of neural tube defects at high doses. Second and third trimesters: Chronic use may lead to neonatal abstinence syndrome (NAS). No increased risk of major malformations in human studies.

Warnings & precautions

■ FDA Black Box Warning

Side Effect Profile

Serious Effects

Absolute Contraindications

Hypersensitivity to buprenorphine or naloxone; severe respiratory insufficiency; severe acute bronchial asthma; paralytic ileus; use in patients with known or suspected gastrointestinal obstruction.