[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [Opioids and antagonists](https://durgical.com/en/pharmacology/classes/opioids-and-antagonists/) › Butorphanol

[Pharmacology](https://durgical.com/en/pharmacology/) · [Opioids and antagonists](https://durgical.com/en/pharmacology/classes/opioids-and-antagonists/)

# Butorphanol

An opioid agonist-antagonist: a partial μ agonist and a full κ agonist. It has a respiratory ceiling but can cause dysphoria and withdrawal.

Updated 2026-11-01

- Class: [Opioids and antagonists](https://durgical.com/en/pharmacology/classes/opioids-and-antagonists/)
- Receptor: κ (agonist) and μ (partial agonist) opioid receptors
- ATC code: N02AF01

## ⚠ High-alert medication

An error with this medicine can cause serious harm: double checks and protocols are used.

◎**κ (agonist) and μ (partial agonist) opioid receptors**Butorphanol

ⓘ The figure shows morphine in the μ receptor; butorphanol occupies the same site. There is no structure of butorphanol in an opioid receptor.

**Target in 3D:** κ (agonist) and μ (partial agonist) opioid receptors. PDB structure 8EF6 (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/8EF6) · Drag to rotate · pinch to zoom

## Mechanism of action

Butorphanol is a partial μ-receptor agonist and a full κ-receptor agonist. κ activation adds to analgesia and sedation, but also to psychotomimetic effects and dysphoria. As a partial μ agonist it antagonises full agonists and can precipitate withdrawal in dependent patients.

- Fully activates the κ receptor
- Only partly activates the μ receptor
- Pain relief and sedation with a ceiling on breathing
- κ activation can cause dysphoria and hallucinations

## Pharmacokinetics

**Absorption**
Injection or nasal spray.

**Metabolism**
Liver, to hydroxybutorphanol; its half-life triples in hepatic impairment.

**Elimination**
Kidney; its half-life doubles in severe renal impairment.

## Indications

- Pain needing an opioid, including labour pain
- Pre-anaesthetic medication and supplement to anaesthesia

## Adverse effects

### Common

- Drowsiness and dizziness
- Nausea and vomiting
- Psychotomimetic effects (dysphoria, hallucinations)

### Serious (rare, important)

- Life-threatening respiratory depression, above all at the start or after a dose increase
- Addiction, abuse and misuse, with risk of overdose and death
- Neonatal opioid withdrawal syndrome with prolonged use in pregnancy
- Higher pulmonary artery pressure and cardiac workload
- Precipitated withdrawal in opioid-dependent patients

## Contraindications

- Significant respiratory depression
- Acute or severe bronchial asthma without monitoring or resuscitation equipment
- Known or suspected gastrointestinal obstruction, including paralytic ileus
- Hypersensitivity to the drug

## Key interactions

**Benzodiazepines, alcohol and other central nervous system depressants**
Add up to profound sedation, respiratory depression, coma and death.

**Full μ agonists (morphine, fentanyl) in use or dependence**
Can weaken their pain relief and precipitate withdrawal in dependent patients.

## What is monitored

- Respiratory rate and sedation
- Mental state: dysphoria or hallucinations
- Blood pressure

## Administration and safety

- Used with caution in acute myocardial infarction, ventricular dysfunction or coronary insufficiency, because it increases cardiac workload.
- In kidney or liver disease the dosing intervals are lengthened.
- Controlled medicine: the order is verified, every dose recorded and leftovers kept secure.

## Nursing care

- Before each dose: respiratory rate, oxygen saturation and sedation level; hold the dose and report excessive sedation or slow breathing.
- Keep naloxone at hand and teach the family to recognise an overdose.
- Ask about opioid use: it can precipitate withdrawal.
- Watch for confusion, dysphoria or hallucinations.

## Pregnancy and breastfeeding

It crosses the placenta; it is used in labour and the newborn is watched for respiratory depression.

## Memory aid

BUTORphanol = «kappa at full throttle»: a full κ agonist (dysphoria) and half a μ agonist (ceiling, precipitated withdrawal). Mind the heart: it raises pulmonary pressure.

## Test yourself

Think of the answer, then tap the question to see it.

## Why can butorphanol cause dysphoria and hallucinations?

Because it is a full κ-receptor agonist, and κ activation produces psychotomimetic effects.

## Why is it used with caution in acute myocardial infarction?

Because it raises pulmonary artery pressure, vascular resistance and cardiac workload.

## What happens if butorphanol is given to a morphine-dependent patient?

As a partial μ agonist it can displace morphine and precipitate withdrawal.

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/pharmacology/butorphanol/)

## Related drugs

- [Nalbuphine](https://durgical.com/en/pharmacology/nalbuphine/)
- [Pentazocine](https://durgical.com/en/pharmacology/pentazocine/)
- [Buprenorphine](https://durgical.com/en/pharmacology/buprenorphine/)

[← Back to the class: Opioids and antagonists](https://durgical.com/en/pharmacology/classes/opioids-and-antagonists/)

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: [Butorphanol Injection: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a682667.html) (MedlinePlus (U.S. National Library of Medicine), 2026); [BUTORPHANOL TARTRATE injection, solution](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=9822ca3f-aee2-46e5-8a96-495400e65d10) (DailyMed (U.S. National Library of Medicine), 2026); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 23 (McGraw Hill, 2023); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=N02AF01) (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake

Representative model, for educational purposes only.

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