[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [Antiseizure medicines](https://durgical.com/en/pharmacology/classes/antiseizure-medicines/) › Carbamazepine

[Pharmacology](https://durgical.com/en/pharmacology/) · [Antiseizure medicines](https://durgical.com/en/pharmacology/classes/antiseizure-medicines/)

# Carbamazepine

An antiseizure medicine that also treats trigeminal neuralgia. It blocks sodium channels and, in some people of Asian ancestry, causes severe skin reactions.

Updated 2026-11-01

- Class: [Antiseizure medicines](https://durgical.com/en/pharmacology/classes/antiseizure-medicines/)
- Ion channel: Voltage-gated sodium channel (Nav)
- ATC code: N03AF01
- WHO Model List of Essential Medicines

⇅**Voltage-gated sodium channel (Nav)**Carbamazepine

ⓘ The figure shows carbamazepine bound to human Nav1.7 (SCN9A), a peripheral sodium channel of the same family as the brain channels (Nav1.1, Nav1.2, Nav1.6) through which it controls seizures.

**Target in 3D:** Voltage-gated sodium channel (Nav). PDB structure 8S9C (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/8S9C) · Drag to rotate · pinch to zoom

## Mechanism of action

Carbamazepine binds voltage-gated sodium channels and holds them in the inactivated state. Neurons that fire rapidly and repeatedly, as in a seizure focus, are blocked most, so the spread of the discharge is limited while normal firing continues. It strongly induces liver enzymes, including those that break it down.

- Binds voltage-gated sodium channels in the neuronal membrane
- Holds the channel in its inactivated state
- Rapid, repetitive firing is blocked first
- The seizure discharge does not spread

## Pharmacokinetics

**Absorption**
Absorbed by mouth; the suspension faster and the extended-release form slower than tablets

**Metabolism**
In the liver, mainly by CYP3A4, to an active epoxide; it induces its own metabolism

**Elimination**
Metabolites in the urine

**Half-life**
Starts at about 25 to 65 hours and falls to about 12 to 17 hours with repeated doses (autoinduction)

## Indications

- Focal (partial) seizures and generalized tonic-clonic seizures [Epilepsy and seizures →](https://durgical.com/en/conditions/epilepsy-and-seizures/)
- Trigeminal neuralgia [Trigeminal neuralgia →](https://durgical.com/en/conditions/trigeminal-neuralgia/)
- Bipolar disorder, acute mania and mixed episodes (extended-release form)

## Adverse effects

### Common

- Dizziness, drowsiness, unsteadiness and double vision
- Nausea and vomiting
- Hyponatraemia, often from inappropriate ADH secretion (SIADH)
- Abnormal liver tests and leukopenia, usually not progressing

### Serious (rare, important)

- Stevens-Johnson syndrome and toxic epidermal necrolysis, linked to HLA-B*1502
- Aplastic anaemia and agranulocytosis
- DRESS (multi-organ hypersensitivity)
- Fetal malformations, including spina bifida

## Contraindications

- History of bone marrow depression
- Hypersensitivity to carbamazepine or to tricyclic compounds
- Use with an MAO inhibitor or within 14 days of stopping one
- Use with nefazodone

## Key interactions

**CYP3A4 inhibitors (azole antifungals, verapamil, protease inhibitors, grapefruit juice)**
Carbamazepine levels rise, with toxicity

**Hormonal contraceptives**
Lower contraceptive levels; contraception can fail

**Lamotrigine, valproate, phenytoin and many other drugs**
Carbamazepine induces their metabolism and lowers their levels

**Absence or atypical absence seizures**
Not controlled; mixed seizure disorders may get worse

## What is monitored

- HLA-B*1502 before starting in people with ancestry from at-risk Asian populations
- Complete blood count before and during treatment
- Serum sodium and liver tests
- Serum carbamazepine level when needed

## Administration and safety

- Given by mouth; tablets, suspension and extended-release forms are absorbed at different speeds and are not swapped without care
- Withdrawn gradually: stopping suddenly can trigger seizures

## Nursing care

- Ask about ancestry and confirm the HLA-B*1502 result before the first dose when indicated
- Teach to report rash, fever, sore throat, mouth ulcers or easy bruising at once
- Watch for confusion, headache or seizures that may signal hyponatraemia
- Warn about drowsiness and dizziness, and about avoiding grapefruit
- Remind that hormonal contraception may fail and another method is needed

## Pregnancy and breastfeeding

Linked to congenital malformations, including spina bifida; the risks and benefits are weighed before and during pregnancy.

## Memory aid

Carbamazepine: «the three Ss» – Sodium channel blocker, SJS with HLA-B*1502, SIADH; and it speeds up its own metabolism.

## Test yourself

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

## Which allele is screened before carbamazepine in people of Asian ancestry?

HLA-B*1502. Carriers have a much higher risk of Stevens-Johnson syndrome and toxic epidermal necrolysis; the label estimates about ten times more risk in some Asian countries.

## Why does the half-life of carbamazepine shorten after the first weeks?

It induces the liver enzymes (mainly CYP3A4) that metabolize it: autoinduction.

## Which electrolyte disorder is typical of carbamazepine?

Hyponatraemia, often caused by inappropriate secretion of antidiuretic hormone (SIADH).

## Which pain syndrome is a classic indication for carbamazepine?

Trigeminal neuralgia.

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

## Related drugs

- [Oxcarbazepine](https://durgical.com/en/pharmacology/oxcarbazepine/)
- [Phenytoin](https://durgical.com/en/pharmacology/phenytoin/)
- [Lamotrigine](https://durgical.com/en/pharmacology/lamotrigine/)

## Related conditions

- [Epilepsy and seizures](https://durgical.com/en/conditions/epilepsy-and-seizures/)
- [Trigeminal neuralgia](https://durgical.com/en/conditions/trigeminal-neuralgia/)

[← Back to the class: Antiseizure medicines](https://durgical.com/en/pharmacology/classes/antiseizure-medicines/)

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

Sources: [Carbamazepine: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a682237.html) (MedlinePlus (U.S. National Library of Medicine), 2026); [DailyMed - CARBAMAZEPINE tablet](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=e68998cb-5f91-4d7e-85a6-555efb8b0384) (DailyMed (U.S. National Library of Medicine), 2026); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=N03AF01) (WHO Collaborating Centre for Drug Statistics Methodology, 2026); [eEML - Electronic Essential Medicines List](https://list.essentialmeds.org/) (World Health Organization, 2025).

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Representative model, for educational purposes only.

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