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

# Pentazocine

A partial μ and κ-agonist opioid. By mouth it is combined with naloxone to prevent injection misuse; at high doses it causes dysphoria.

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: N02AD01

## ⚠ 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**Pentazocine

ⓘ The figure shows morphine in the μ receptor; pentazocine occupies the same site. The only available pentazocine structure is in the sigma-1 receptor, which is not its analgesic target.

**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

Pentazocine is a partial μ-receptor agonist and a κ-receptor agonist. It produces pain relief, sedation and respiratory depression with a ceiling effect; at high doses κ activation causes dysphoria and psychotomimetic effects. Tablets combine it with naloxone: by mouth naloxone hardly acts, but if the product is injected it blocks pentazocine's effect.

- Partly activates the μ receptor and activates the κ receptor
- Pain relief with a ceiling on breathing
- At high doses κ activation causes dysphoria
- The tablet's naloxone acts only if injected: it deters misuse

## Pharmacokinetics

**Absorption**
By mouth, combined with naloxone.

## Indications

- Pain needing an opioid when other options are not enough

## Adverse effects

### Common

- Dizziness and drowsiness
- Nausea and vomiting
- Dysphoria and hallucinations at high doses

### 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

## 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

## Administration and safety

- The tablet contains naloxone to prevent injection use; it is not dissolved or injected.
- 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 for confusion, dysphoria or hallucinations.
- Ask about other opioid use: it can precipitate withdrawal.

## Pregnancy and breastfeeding

Prolonged use in pregnancy can cause neonatal opioid withdrawal syndrome, which is expected and treatable; the newborn is watched after birth.

## Memory aid

PENTAZOcine with naloxone = «a tablet with a padlock»: it works by mouth; injected, the naloxone locks the receptor.

## Test yourself

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

## Why do pentazocine tablets contain naloxone?

To prevent misuse by injection: by mouth naloxone hardly acts, but injected it blocks pentazocine's effect.

## Which receptor explains pentazocine's dysphoria at high doses?

The κ receptor, at which it is an agonist.

## What kind of action does pentazocine have at the μ receptor?

It is a partial agonist, with a ceiling for pain relief and respiratory depression.

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

## Related drugs

- [Butorphanol](https://durgical.com/en/pharmacology/butorphanol/)
- [Nalbuphine](https://durgical.com/en/pharmacology/nalbuphine/)
- [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: [Pentazocine and Naloxone: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a625096.html) (MedlinePlus (U.S. National Library of Medicine), 2026); [PENTAZOCINE AND NALOXONE tablet](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=41ebdaaf-3bbc-419f-b996-0341efc14623) (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=N02AD01) (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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