Pharmacology · 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
The figure shows naloxone, to which nalbuphine is chemically related, in the inactive μ receptor; nalbuphine occupies the same site.
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
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.
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.
Related drugs
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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 (MedlinePlus (U.S. National Library of Medicine), 2026); NALBUPHINE HYDROCHLORIDE injection, solution (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 (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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Representative model, for educational purposes only.