Lamotrigine
Class: Broad-spectrum antiepileptic, phenyltriazine derivative
Indications
- Focal (partial) seizures
- Generalized tonic-clonic seizures
- Absence seizures (alternative to ethosuximide/valproate)
- Lennox–Gastaut syndrome
- Bipolar disorder (maintenance therapy)
Mechanism of Action
- Blocks voltage-gated sodium channels → reduces glutamate release
- Stabilizes neuronal membranes
- Broad-spectrum antiepileptic activity
Dosage
- Adults (without valproate): Start 25 mg once daily for 2 weeks → 50 mg/day (weeks 3–4) → increase by 50 mg every 1–2 weeks; maintenance 225–375 mg/day in 2 doses
- Adults (with valproate): Start 25 mg every other day for 2 weeks → 25 mg daily (weeks 3–4) → titrate slowly; maintenance 100–200 mg/day
- Children: Weight-based dosing; titrate cautiously to avoid rash
Major Side Effects
- Dizziness, headache, diplopia, ataxia
- GI upset (nausea, vomiting)
- Insomnia
- Serious: Stevens–Johnson syndrome, toxic epidermal necrolysis (especially if titrated too quickly)
- Hypersensitivity reactions (multiorgan failure, rare)
Contraindications
- Hypersensitivity to lamotrigine
- History of severe cutaneous adverse reactions with lamotrigine
Compatible Solvent / Administration
- Oral tablets, chewable tablets, dispersible tablets
- Administer with or without food
Special Precautions
- Titrate slowly to minimize risk of severe rash
- Monitor for mood changes, suicidality (especially in bipolar patients)
- Drug interactions: valproate ↑ lamotrigine levels; enzyme inducers (carbamazepine, phenytoin) ↓ lamotrigine levels
- Pregnancy Category C – clearance increases during pregnancy
Key Point: Lamotrigine is a versatile and well-tolerated AED, also used in bipolar disorder, but must be titrated slowly due to the risk of life-threatening rash.