Lamotrigine (Lamictal): Uses, Dosage, Side Effects, and What to Expect

Lamotrigine (brand name: Lamictal) is a anticonvulsant / mood stabilizer. Lamotrigine stabilizes neuronal membranes by blocking voltage-sensitive sodium channels, which inhibits the release of excitatory neurotransmitters (primarily glutamate). It may also modulate calcium channels. Unlike lithium and valproate, lamotrigine is more effective at preventing depressive episodes than manic episodes in bipolar disorder, making it particularly valuable for patients whose illness is predominantly depressive.

• Bipolar I Disorder (maintenance — prevention of mood episodes)
• Epilepsy (partial seizures, generalized tonic-clonic seizures, Lennox-Gastaut syndrome)

Common off-label uses:

• Bipolar II Disorder
• Bipolar depression (acute)
• Treatment-resistant depression (augmentation)
• Borderline personality disorder
• PTSD

Requires very slow titration to minimize rash risk. Without valproate: start 25 mg/day for 2 weeks, then 50 mg/day for 2 weeks, then increase by 50 mg/week to target 200 mg/day. With valproate: halve all doses (valproate doubles lamotrigine levels). With enzyme inducers (carbamazepine): double all doses. Target: 100-400 mg/day for bipolar maintenance.

Effects on mood stabilization emerge over weeks as the dose is slowly titrated to therapeutic range. Full therapeutic effect at target dose takes 4-8 weeks.

• Headache
• Dizziness
• Nausea
• Blurred or double vision
• Coordination problems
• Insomnia
• Rash (benign, 8-10% of patients)

• Stevens-Johnson syndrome / Toxic Epidermal Necrolysis (SJS/TEN) — potentially fatal skin reaction occurring in ~0.1% of adult patients, higher in children. Risk is highest during the first 8 weeks and with rapid dose escalation. Any rash should prompt immediate medical evaluation.
• Aseptic meningitis (rare)
• Blood dyscrasias (rare)
• Multiorgan hypersensitivity (DRESS syndrome)

Valproate approximately doubles lamotrigine levels (requires half dosing). Carbamazepine, phenytoin, and other enzyme inducers halve lamotrigine levels (requires double dosing). Oral contraceptives can decrease lamotrigine levels by ~50% — dose adjustments may be needed when starting or stopping birth control.

Lamotrigine has more safety data in pregnancy than most mood stabilizers. It is often considered the preferred mood stabilizer during pregnancy. However, lamotrigine levels drop significantly during pregnancy (up to 65%) due to increased glucuronidation, often requiring dose increases. Levels normalize quickly after delivery, requiring prompt dose reduction.

Taper gradually over at least 2 weeks to avoid seizure risk (even in non-epileptic patients).