[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [Barbiturates](https://durgical.com/en/pharmacology/classes/barbiturates/) › Pentobarbital

# Pentobarbital

## Barbiturates?

Barbiturates

## High alert?

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

## Pregnancy: avoid?

Avoided when possible: barbiturates cross the placenta and can harm the fetus; use near delivery can depress the newborn's breathing and cause withdrawal.

A short-acting barbiturate given by injection for refractory seizures and sedation. Strongly alkaline, habit-forming and deadly in overdose.

Updated Nov 12, 2026

## Quick facts

**Group**
[Barbiturates](https://durgical.com/en/pharmacology/classes/barbiturates/)

**Target**
GABA-A receptor (barbiturate site)

**Used for**
Emergency control of acute convulsions

**Key effects**
Drowsiness · Paradoxical excitement

**Monitor**
Breathing · Blood pressure and heart rate

**ATC**
N05CA01

No doses: the clinician sets them by the current guideline.

On this page

- The basics Mechanism of action
- Indications
- Adverse effects
- Pharmacokinetics
- Memory aid

- Clinical What the labels mean

- Safety Contraindications
- Key interactions
- What is monitored
- Administration and safety
- Pregnancy and breastfeeding
- Nursing care

- Study Test yourself

- Connections Connections

## Mechanism of action

◎**GABA-A receptor (barbiturate site)**Pentobarbital

ⓘ No structure of pentobarbital in the GABA-A receptor is available; the figure shows phenobarbital, another barbiturate at the same site, in the human α1β2γ2 receptor with GABA.

**Target in 3D:** GABA-A receptor (barbiturate site). PDB structure 6X3W (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/6X3W) · Drag to rotate · pinch to zoom

Pentobarbital binds a barbiturate site on the GABA-A receptor and keeps its chloride channel open longer each time GABA binds; at higher concentrations it opens the channel directly, even without GABA, and also reduces glutamate excitation. Neurons are hyperpolarised and the whole CNS is depressed in a dose-related way: sedation, sleep, anaesthesia, then coma with depression of breathing. Because the effect does not stop at a ceiling, as with benzodiazepines, overdose is far more dangerous. It also induces liver enzymes.

- Binds the barbiturate site of GABA-A
- Chloride channel stays open longer; opens directly at high levels
- Dose-related CNS depression: sedation to coma
- No ceiling: breathing can stop in overdose

## Indications

- Emergency control of acute convulsions (status epilepticus, eclampsia, toxic reactions), including induced coma for refractory status epilepticus [Status epilepticus →](https://durgical.com/en/conditions/status-epilepticus/)
- Sedation and preanaesthetic use; induced coma to lower raised intracranial pressure [Raised intracranial pressure and brain herniation →](https://durgical.com/en/conditions/raised-intracranial-pressure-and-brain-herniation/)
- Short-term treatment of insomnia (largely replaced) [Insomnia disorder →](https://durgical.com/en/conditions/insomnia-disorder/)

## Adverse effects

### Common

- Drowsiness, hangover, confusion
- Paradoxical excitement (older people, children, people in pain)
- Low blood pressure
- Pain at the injection site

### Serious (rare, important)

- Respiratory depression, apnoea and laryngospasm, especially with fast injection
- Tissue necrosis if it leaks; gangrene after accidental intra-arterial injection
- Dependence, with delirium, seizures and possibly death on sudden withdrawal
- Overdose: coma, hypotension, hypothermia, shock and death

## Contraindications

- Known barbiturate sensitivity
- Manifest or latent porphyria

## Key interactions

**Alcohol, opioids, benzodiazepines and other CNS depressants**
Additive, potentially fatal CNS and respiratory depression.

**Warfarin, corticosteroids, oral contraceptives and other enzyme substrates**
Enzyme induction lowers their effect; another contraceptive method may be needed.

**Valproate and MAO inhibitors**
Raise or prolong barbiturate effects.

**Phenytoin**
Unpredictable effect on phenytoin levels; levels are checked more often.

## What is monitored

- Breathing, oxygen saturation and airway; ventilatory support ready
- Blood pressure and heart rate
- EEG when used for induced coma
- Injection site, and limb pain during injection

## Administration and safety

- Given slowly intravenously; fast injection causes apnoea and hypotension.
- Strongly alkaline: not mixed with other drugs or solutions; cloudy or precipitated solution is discarded.
- Into a large vein; the injection is stopped at once if the patient feels pain in the limb (risk of intra-arterial injection).
- Used only where airway support and ventilation are available.

## Pregnancy and breastfeeding

Avoided when possible: barbiturates cross the placenta and can harm the fetus; use near delivery can depress the newborn's breathing and cause withdrawal.

## Nursing care

- Before: check airway equipment, IV access patency and porphyria history.
- During: monitor breathing, saturation and blood pressure continuously.
- Watch the site for swelling or pallor; stop for pain.
- After prolonged use: taper rather than stop abruptly; watch for withdrawal.

## Pharmacokinetics

**Absorption**
Injection, usually intravenous; also intramuscular.

**Metabolism**
Liver microsomal enzymes; metabolites excreted in the urine. It also induces these enzymes.

**Half-life**
Long and dose-dependent (roughly 15 to 50 hours in adults).

**Onset and duration**
Almost immediate after intravenous injection.

## Memory aid

Barbiturates DURATE (prolong the duration of chloride opening); benzodiazepines FREQUENT (increase the frequency).

## Test yourself

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

## How does a barbiturate differ from a benzodiazepine at the GABA-A receptor?

It prolongs each channel opening and can open the channel directly at high levels; benzodiazepines only increase opening frequency when GABA is present.

## Why is pentobarbital overdose more dangerous than benzodiazepine overdose?

There is no ceiling: increasing doses deepen CNS and respiratory depression to coma and death.

## Which inherited condition is a contraindication to barbiturates?

Porphyria (barbiturates induce ALA synthase).

## Why must pentobarbital not leak out of the vein?

The solution is strongly alkaline and causes tissue necrosis; intra-arterial injection can cause gangrene.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/pharmacology/pentobarbital/)

[More Pharmacology questions →](https://durgical.com/en/practice/?f=pharmacology)

## What the labels mean

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

**Pregnancy: avoid**
Avoided when possible: barbiturates cross the placenta and can harm the fetus; use near delivery can depress the newborn's breathing and cause withdrawal.

## Connections

## Related drugs 4

- [Phenobarbital](https://durgical.com/en/pharmacology/phenobarbital/)
- [Thiopental](https://durgical.com/en/pharmacology/thiopental/)
- [Midazolam](https://durgical.com/en/pharmacology/midazolam/)
- [Propofol](https://durgical.com/en/pharmacology/propofol/)

## Related conditions 3

- [Status epilepticus](https://durgical.com/en/conditions/status-epilepticus/)
- [Raised intracranial pressure and brain herniation](https://durgical.com/en/conditions/raised-intracranial-pressure-and-brain-herniation/)
- [Insomnia disorder](https://durgical.com/en/conditions/insomnia-disorder/)

[← Back to the class: Barbiturates](https://durgical.com/en/pharmacology/classes/barbiturates/)

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

Sources: [PENTOBARBITAL SODIUM injection, solution](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=d375b92a-baa1-4d63-9ad1-1467dcfde7d5) (DailyMed (U.S. National Library of Medicine), 2026); [Human GABAA receptor alpha1-beta2-gamma2 subtype in complex with GABA plus phenobarbital](https://www.rcsb.org/structure/6X3W) (RCSB Protein Data Bank, 2020); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=N05CA01) (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

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Representative model, for educational purposes only.

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