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
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

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 →
Trigeminal neuralgia 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

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.

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.

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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: Carbamazepine: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); DailyMed - CARBAMAZEPINE tablet (DailyMed (U.S. National Library of Medicine), 2026); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026); eEML - Electronic Essential Medicines List (World Health Organization, 2025).

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Representative model, for educational purposes only.