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

# Nalbuphine

An injectable κ-agonist, μ-antagonist opioid. It has a respiratory ceiling and can partly reverse μ-agonist respiratory depression, but precipitates withdrawal.

Updated 2026-11-01

- Class: [Opioids and antagonists](https://durgical.com/en/pharmacology/classes/opioids-and-antagonists/)
- Receptor: κ (agonist) and μ (antagonist) opioid receptors
- ATC code: N02AF02

## ⚠ High-alert medication

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

◎**κ (agonist) and μ (antagonist) opioid receptors**Nalbuphine

ⓘ The figure shows naloxone, to which nalbuphine is chemically related, in the inactive μ receptor; nalbuphine occupies the same site.

**Target in 3D:** κ (agonist) and μ (antagonist) opioid receptors. PDB structure 9BJK (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/9BJK) · Drag to rotate · pinch to zoom

## Mechanism of action

Nalbuphine, chemically related to naloxone and oxymorphone, is a κ-receptor agonist and a μ-receptor antagonist. κ activation produces pain relief; μ blockade explains its ceiling on respiratory depression and why, given after a μ agonist, it can partly reverse the respiratory depression that agonist causes. Naloxone reverses its own effects.

- Activates the κ receptor: pain relief
- Blocks the μ receptor
- A ceiling on respiratory depression
- After a μ agonist: partly reverses depression or precipitates withdrawal

## Pharmacokinetics

**Absorption**
Given intravenously, intramuscularly or subcutaneously.

**Metabolism**
Liver.

**Half-life**
About 5 hours; pain relief lasts 3 to 6 hours.

## Indications

- Pain needing an opioid
- Obstetric analgesia during labour and delivery
- Supplement to balanced anaesthesia and pre- and postoperative analgesia

## Adverse effects

### Common

- Sedation
- Sweating
- Nausea and vomiting
- Itching, flushing and orthostatic hypotension from histamine release

### 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
- Precipitated withdrawal in opioid-dependent patients
- Bradycardia during anaesthesia

## 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.

**Naloxone**
Reverses the respiratory depression caused by nalbuphine.

## What is monitored

- Respiratory rate and sedation
- Heart rate and blood pressure
- In labour: fetal heart rate and the newborn's breathing

## Administration and safety

- It can be given intravenously, intramuscularly or subcutaneously.
- Before giving it, ask about opioid use so as not to precipitate withdrawal.
- 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.
- Watch the heart rate, above all in the surgical setting.
- In obstetric analgesia, watch the fetus and the newborn.

## Pregnancy and breastfeeding

It is used in labour; it can affect the fetal heart rate and depress the newborn's breathing, so both are watched.

## Memory aid

NALbuphine = «NAL» as in NALoxone: a relative of the antagonist. It blocks μ (ceiling, withdrawal) and activates κ (pain relief).

## Test yourself

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

## What does nalbuphine do at each opioid receptor?

It is a κ-receptor agonist and a μ-receptor antagonist.

## What can happen if nalbuphine is given to a patient who received morphine?

It can partly reverse morphine's respiratory depression and, if the patient is dependent, precipitate withdrawal.

## Does naloxone reverse nalbuphine's respiratory depression?

Yes; although it is an agonist-antagonist, its respiratory depressant effects are reversed by naloxone.

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

## Related drugs

- [Butorphanol](https://durgical.com/en/pharmacology/butorphanol/)
- [Pentazocine](https://durgical.com/en/pharmacology/pentazocine/)
- [Naloxone](https://durgical.com/en/pharmacology/naloxone/)

[← 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: [Nalbuphine Injection: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a682668.html) (MedlinePlus (U.S. National Library of Medicine), 2026); [NALBUPHINE HYDROCHLORIDE injection, solution](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=a99fe500-f52b-483c-807c-178f1a78a02b) (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=N02AF02) (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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