Lamotrigine
A phenyltriazine antiepileptic for focal and generalized seizures, including Lennox-Gastaut syndrome, and to prevent bipolar depression.
Drug card
- How it works
- Blocking neuronal sodium channels to stop rapid, repetitive firing
- Used for
- Focal, tonic-clonic and Lennox-Gastaut seizures
- Typical absence seizures in children
- Bipolar I disorder, to prevent mood episodes
- Known for
- Serious rash (SJS, TEN), mostly in weeks 2 to 8
Study it as a flashcard, and it comes back before you forget it.
Mechanism of action
How does lamotrigine work?
Lamotrigine, a phenyltriazine, is thought to inhibit voltage-sensitive sodium channels, steadying neuronal membranes and reducing release of excitatory amino acids such as glutamate. It is cleared by glucuronidation, which valproate inhibits and which estrogen-containing contraceptives and enzyme inducers speed up.
Like other sodium channel-blocking antiepileptics: These drugs block voltage-gated sodium channels in neurons in a use- and voltage-dependent way: the faster a neuron fires, the more channels they block. Ordinary signaling carries on, but the sustained high-frequency bursts that spread a seizure are cut short. Phenytoin and carbamazepine are also strong inducers of liver enzymes, so they speed the breakdown of many other drugs.
Uses
What is lamotrigine used for?
- Focal, tonic-clonic and Lennox-Gastaut seizures
- Typical absence seizures in children
- Bipolar I disorder, to prevent mood episodes
Side effects
Side effects of lamotrigine
- Serious rash (SJS, TEN), mostly in weeks 2 to 8Known forSerious
- Milder rash
- Dizziness
- Headache
- Double or blurred vision
- Unsteadiness (ataxia)
- Nausea and vomiting
- Drowsiness
- Multiorgan hypersensitivity (DRESS)Serious
- Arrhythmias in structural heart diseaseSerious
- Blood disorders, such as low white cells or plateletsSerious
- Suicidal thoughtsSerious
Known for marks what an exam expects you to know it for.
Watch for
Cautions and what sets it apart
- Start low and go slowly: high starting doses, fast increases and valproate all raise the risk of serious rash.
- Any new rash means stopping it, unless something else clearly explains the rash.
- Valproate more than doubles its level; estrogen-containing contraceptives, phenytoin and carbamazepine lower it.
- It has class IB antiarrhythmic activity and can cause arrhythmias in people with structural heart disease.
Good to know: Its serious rash risk is highest in children and in the first 2 to 8 weeks, which is why the dose is built up over several weeks.
Remember it
A way to remember it
Sodium channel blockers let single shots through but jam the machine gun.
Their block grows with each firing, so ordinary signals pass while the rapid, repetitive bursts of a seizure are stopped.
Written for biofideX
Its class
Sodium channel-blocking antiepileptics
Other sodium channel-blocking antiepileptics with a card:
Easily mixed up with local anesthetics, valproate and succinimides.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- Lamotrigine orally disintegrating tablets: label (DailyMed)
- Lamotrigine 25 mg tablets: SmPC (emc)
- Lamotrigine (NCI Thesaurus)
- Lamotrigine (NHS)
For learning pharmacology, not for treatment decisions: no doses are given, and a prescriber, pharmacist or the product's own label is the word on any one patient. Spotted a mistake? Tell us and we'll correct it.
Epilepsy and nerve pain
Lamotrigine is one of 8 drugs practiced together here: their classes, how they work, what they treat and what they're known for.
Start Practicing