====== Buprenorphine (Subutex®, Suboxone®, Butrans®) ======

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<WRAP infobox>
^ Buprenorphine | {{ :neuro:opioids:buprenorphine.svg?200 |}} |
| Brand Names | Subutex®, Suboxone®, Butrans®, Sublocade® |
| Drug Class | [[neuro:opioids:start|Opioid]] (Partial μ-agonist) |
| Primary Indication | Opioid Use Disorder, Chronic Pain |
| Receptor Activity | Partial μ agonist; κ antagonist |
| Ceiling Effect | Yes (respiratory depression) |
| Relative Potency | High receptor affinity |
| Controlled Substance | Schedule III |
| FDA Approval | 1985 (analgesic), 2002 (OUD) |
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</WRAP>

===== Overview =====

Buprenorphine is a partial μ-opioid receptor agonist with very high receptor affinity and slow dissociation.

It is used for both chronic pain and treatment of opioid use disorder (MOUD).

Because it is a partial agonist, it produces a ceiling effect on respiratory depression and euphoria, making it safer than full μ agonists.

However, its high receptor affinity can displace full agonists and precipitate withdrawal.

<WRAP clear></WRAP>

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===== Mechanism of Action =====

**Receptor Activity**
  * Partial μ-opioid receptor agonist  
  * κ-opioid receptor antagonist  
  * Very high receptor affinity  

**Clinical Consequences**
  * Produces analgesia  
  * Ceiling effect on respiratory depression  
  * Can displace morphine, heroin, fentanyl  

High receptor affinity explains precipitated withdrawal risk.

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===== Indications =====

  * Opioid Use Disorder (MOUD)  
  * Chronic pain (transdermal or buccal formulations)  
  * Acute pain (limited use)

Common formulations:
  * Sublingual (Subutex®, Suboxone®)
  * Transdermal patch (Butrans®)
  * Monthly injection (Sublocade®)

Suboxone® = buprenorphine + naloxone (to deter misuse).

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<WRAP contra>
===== Contraindications =====

Absolute:
  * Severe respiratory depression  
  * Acute severe bronchial asthma  

Relative / Caution:
  * Hepatic impairment  
  * Concurrent CNS depressants  
  * Initiation too soon after full opioid use (withdrawal risk)  

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<WRAP details>
===== Dosing =====

Opioid Use Disorder (sublingual):
  * Initial: 2–4 mg  
  * Titrate to 8–16 mg/day (typical maintenance)  

Chronic pain (transdermal):
  * Applied every 7 days  

Initiation requires mild withdrawal state to avoid precipitated withdrawal.

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<WRAP details>
===== Pharmacokinetics =====

Absorption:
  * Sublingual  
  * Buccal  
  * Transdermal  
  * Injectable  

Metabolism:
  * Hepatic (CYP3A4)  

Half-life:
  * ~24–42 hours  

Elimination:
  * Biliary and renal  

Long half-life supports once-daily dosing in OUD.

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<WRAP details>
===== Adverse Effects =====

Common:
  * Nausea  
  * Headache  
  * Constipation  
  * Insomnia  

Serious:
  * Respiratory depression (less than full agonists)  
  * Precipitated withdrawal  
  * Hepatic enzyme elevation  

Lower abuse potential compared to full agonists.

</WRAP>

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<WRAP details>
===== Drug Interactions =====

CNS depressants:
  * Benzodiazepines  
  * Alcohol  
  * Other opioids  

CYP3A4 inhibitors:
  * Azoles  
  * Macrolides  

Risk:
  * Increased sedation  
  * Respiratory depression  

</WRAP>

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<WRAP monitoring>
===== Monitoring =====

Clinical:
  * Withdrawal symptoms during induction  
  * Cravings (OUD patients)  
  * Sedation and respiratory status  

Laboratory:
  * Liver function tests (periodically)  

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<WRAP pearls>
===== Clinical Pearls =====

  * Partial μ agonist → ceiling effect on respiratory depression.  
  * High receptor affinity → can precipitate withdrawal.  
  * Must initiate when patient is in mild withdrawal.  
  * Suboxone® contains naloxone to deter IV misuse.  
  * Schedule III (lower abuse potential than Schedule II opioids).  
  * First-line therapy for opioid use disorder.  

</WRAP>

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===== Toxicity =====

Overdose:
  * Less severe respiratory depression than full agonists  
  * May require higher naloxone doses due to receptor affinity  

Treatment:
  * [[neuro:opioids:naloxone|Naloxone]] (may need repeated dosing)

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===== Comparison Within Class =====

Compared to [[neuro:opioids:morphine|Morphine]]:
  * Partial agonist vs full agonist  
  * Ceiling effect  
  * Safer respiratory profile  

Compared to [[neuro:opioids:methadone|Methadone]]:
  * Lower overdose risk  
  * Less QT prolongation  
  * Requires withdrawal before initiation  

Compared to [[neuro:opioids:naltrexone|Naltrexone]]:
  * Partial agonist vs pure antagonist  
  * Does not block all opioid effects  

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===== Related =====

  * [[neuro:opioids:start|Opioids]]
  * [[neuro:opioids:methadone|Methadone]]
  * [[neuro:opioids:naltrexone|Naltrexone]]
  * [[neuro:opioids:naloxone|Naloxone]]