Pharmacology · Antiseizure medicines
Lamotrigine !
A broad-spectrum antiseizure medicine and bipolar mood stabilizer. It is started very slowly because it can cause a life-threatening rash.
Updated 2026-11-01
The figure shows lamotrigine bound to human Nav1.7 (SCN9A), a peripheral sodium channel of the same family as the brain channels it acts on in epilepsy.
Mechanism of action
Lamotrigine blocks voltage-gated sodium channels, which stabilizes neuronal membranes and reduces the release of excitatory neurotransmitters such as glutamate. It is effective against focal and generalized seizures and helps prevent depressive episodes in bipolar disorder.
- Blocks voltage-gated sodium channels
- Neuronal membranes become more stable
- Less glutamate is released at the synapse
- Seizures and mood episodes become less frequent
Pharmacokinetics
- Absorption
- Rapidly and almost completely absorbed by mouth; food does not change it
- Metabolism
- In the liver, mainly by glucuronidation; inducers speed it up and valproate slows it
- Elimination
- Glucuronide in the urine
- Half-life
- Varies a lot with other medicines: shorter with enzyme inducers, longer with valproate
Indications
- Focal seizures, generalized tonic-clonic seizures and seizures of Lennox-Gastaut syndrome Epilepsy and seizures →
- Maintenance treatment of bipolar I disorder
Adverse effects
Common
- Dizziness, headache, double or blurred vision
- Unsteadiness and drowsiness
- Nausea
- Benign rash
Contraindications
- Previous hypersensitivity to lamotrigine (rash, angioedema, urticaria, mucosal ulcers)
Key interactions
- Valproate
- Lamotrigine levels and half-life rise; higher risk of serious rash
- Estrogen-containing contraceptives
- Lower lamotrigine levels; starting or stopping them changes the dose needed
- Enzyme inducers (carbamazepine, phenytoin, phenobarbital)
- Faster glucuronidation and lower lamotrigine levels
- Other sodium channel blockers
- Higher risk of arrhythmia
What is monitored
- Skin and mucous membranes, especially in the first weeks
- Signs of systemic inflammation (fever, rash, large glands)
- Seizure control when other medicines or contraceptives change
- Mood and suicidal thoughts
Administration and safety
- Given by mouth with a slow, stepwise start; exceeding the starting schedule raises the risk of rash
- Name confusion with other medicines has caused dispensing errors: check the tablet received
- If it was stopped for a long time, the slow start is repeated
Nursing care
- Teach to report any rash, fever, blisters or mouth sores at once
- Check every new medicine or contraceptive for interactions
- Ask about pregnancy plans, since levels can change in pregnancy
- Teach not to stop suddenly
Pregnancy and breastfeeding
Levels can change during pregnancy and the effect may vary; in animals it lowered fetal folate. It is followed by a specialist during pregnancy.
Test yourself
Think of the answer, then tap the question to see it.
Why is lamotrigine started with a slow, stepwise schedule?
Going faster than the starting schedule raises the risk of serious rash, including Stevens-Johnson syndrome and toxic epidermal necrolysis.
Which antiseizure medicine doubles the problem with lamotrigine rash, and why?
Valproate: it inhibits lamotrigine glucuronidation, so lamotrigine levels and half-life rise and rash is more likely.
Besides epilepsy, which psychiatric illness is a main indication of lamotrigine?
Bipolar I disorder, as maintenance treatment to delay mood episodes.
What happens to lamotrigine levels when a woman starts an estrogen-containing contraceptive?
They fall, because estrogens speed up its glucuronidation; seizure control can be lost unless the dose is adjusted.
Related drugs
Related conditions
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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: Lamotrigine: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2021); DailyMed - LAMOTRIGINE 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.