[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [Intravenous anaesthetics](https://durgical.com/en/pharmacology/classes/intravenous-anaesthetics/) › Methohexital

# Methohexital

## Intravenous anaesthetics?

Intravenous anaesthetics

## High alert?

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

Ultra-short-acting barbiturate for anaesthesia induction, classically for electroconvulsive therapy. Contraindicated in porphyria.

Updated Nov 1, 2026

Also called: Methohexital sodium, Methohexitone

## Quick facts

**Group**
[Intravenous anaesthetics](https://durgical.com/en/pharmacology/classes/intravenous-anaesthetics/)

**Target**
GABA-A receptor

**Used for**
Intravenous induction

**Key effects**
Hiccups · Pain on injection · Nausea and vomiting

**Monitor**
Continuous pulse oximetry · ECG and blood pressure

**ATC**
N01AF01

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**Methohexital

ⓘ There is no structure with methohexital. The figure shows phenobarbital, another barbiturate, bound to the human α1β2γ2 GABA-A receptor with GABA.

**Target in 3D:** GABA-A receptor. 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

Methohexital is an oxybarbiturate (it has no sulfur) that enhances and, at higher levels, directly activates GABA-A receptors, increasing chloride entry and depressing the brain. It reaches the brain within seconds and its effect after a single dose ends by redistribution to other tissues. It is cleared faster than thiopental and accumulates less, so recovery is quicker. It gives little analgesia and, unlike most anaesthetics, can increase seizure activity, which suits electroconvulsive therapy.

- Rapid entry into the brain after intravenous injection
- Potentiates GABA-A receptors: more chloride, neuronal depression
- Loss of consciousness; effect ended by redistribution
- Faster hepatic clearance than thiopental: quick recovery

## Indications

- Intravenous induction of general anaesthesia and anaesthesia for short procedures with little painful stimulus
- Anaesthesia for electroconvulsive therapy, together with a neuromuscular blocker
- Rectal or intramuscular induction in children older than one month

## Adverse effects

### Common

- Hiccups, coughing and muscle twitching
- Pain on injection, more than with thiopental
- Transient hypotension and tachycardia
- Nausea and vomiting, emergence delirium

### Serious (rare, important)

- Respiratory depression and apnoea, laryngospasm, bronchospasm, cardiorespiratory arrest
- Seizures, especially in patients with a history of partial seizures
- Intra-arterial injection: thrombosis, necrosis and gangrene
- Acute porphyria attacks in susceptible patients

## Contraindications

- Latent or manifest porphyria
- Known hypersensitivity to barbiturates
- Situations in which general anaesthesia is contraindicated

## Key interactions

**Chronic barbiturates or phenytoin**
Reduced effectiveness of methohexital.

**Phenytoin, anticoagulants, corticosteroids and alcohol**
Barbiturates can change the metabolism of these drugs.

**Lactated Ringer's solution**
Incompatible as a diluent.

## What is monitored

- Continuous pulse oximetry, airway and ventilation
- ECG and blood pressure
- Injection site: pain, blanching or swelling suggesting extravasation or arterial placement
- Seizure activity

## Administration and safety

- Used only where respiratory and cardiac function are monitored continuously, with resuscitation drugs and airway equipment at hand.
- Reconstituted with compatible diluents (sterile water, dextrose or saline), never Lactated Ringer's; the alkaline solution is incompatible with many acidic drugs.
- Inject into a free-flowing vein; stop at once if pain, extravasation or arterial placement is suspected.
- Rectal and intramuscular routes are reserved for children, with the same monitoring.

## Pregnancy and breastfeeding

Animal studies showed no developmental harm, and human data are lacking; prolonged or repeated anaesthetic exposure late in pregnancy or in young children raises concern for the developing brain.

## Nursing care

- Before induction, ask about porphyria and previous reactions to barbiturates.
- Prepare oxygen, bag-mask, suction and intubation equipment.
- Watch the cannula site during injection for pain or blanching of the hand.
- After the procedure, monitor breathing and consciousness until fully awake.

## Pharmacokinetics

**Distribution**
Very rapid uptake by the brain, then redistribution; it concentrates in fat less than thiobarbiturates.

**Metabolism**
Hepatic, by demethylation and side-chain oxidation.

**Elimination**
Kidney, by glomerular filtration of metabolites.

**Onset and duration**
Within seconds intravenously; slower by intramuscular or rectal routes in children.

## Memory aid

METHOhexital, the «ECT barbiturate»: short, sulfur-free, makes seizures easier, and never in porphyria.

## Test yourself

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

## Why is methohexital a good choice for electroconvulsive therapy anaesthesia?

It is ultra-short acting and, unlike most anaesthetics, can increase seizure activity.

## Which metabolic disease contraindicates methohexital?

Porphyria, latent or manifest, because barbiturates can trigger acute attacks.

## What is the danger of intra-arterial injection of methohexital?

Thrombosis distal to the injection, with necrosis that may progress to gangrene.

## Why do patients wake faster after methohexital than after thiopental?

It is cleared faster by the liver and concentrates less in fat, so it accumulates less.

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[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.

## Connections

## Related drugs 3

- [Thiopental](https://durgical.com/en/pharmacology/thiopental/)
- [Propofol](https://durgical.com/en/pharmacology/propofol/)
- [Suxamethonium](https://durgical.com/en/pharmacology/suxamethonium/)

[← Back to the class: Intravenous anaesthetics](https://durgical.com/en/pharmacology/classes/intravenous-anaesthetics/)

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

Sources: [DailyMed - METHOHEXITAL SODIUM injection](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=f76d4ab9-2f6c-420b-afec-b9cdfdc083ce) (DailyMed (U.S. National Library of Medicine), 2026); [RCSB PDB - 6X3W: 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=N01AF01) (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

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Representative model, for educational purposes only.

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