Lamotrigine (Lamictal)

Anticonvulsant (glutamate voltage-gated sodium channel blocker)

Dosing

Usual titration is 25mg/d x 2wk, 50mg/d x 2wk, then 100mg/d. For patients under age 18 or on Depakote, start 25mg qod x 2wk, 25mg/d x 2wk then 50 mg/d. For patients on carbamazepine, phenytoin, phenobarbital, or primidone, start 50mg/d x 2wk, 100mg/d x 2wk, then 200 mg/d.

> Targets after titration (mg/d): Adults (100-250), geriatrics (50-150), children <12 (50-150), third trimester pregnancy (150-400). CBZ and estrogen-OCPs lowers it 40-50%, VPA doubles it, oxcarbazepine at > 1200 mg/d lowers it 30-50%. Lamotrigine may lower quetiapine levels 30%. Folic acid interferes with lamotrigine (but other folates do now). Serum levels not necessary but usually are 2-6 mg/l.

Management

Warn of severe rash (1/3000 chance, but have to stop if any rash in first 3 months, and 10% chance of benign rash). Signs of severe rash = face, lips, palms, feet, blistering, raised, fever, systemic signs, High eosinophils/LFTs. If rash was mild, can retitrate super slow in 1 month (start 5mg/d, raise by 5mg q2weeks to 25mg then use usual titration).

Retitrate if off lamictal for > 7 day. Nausea, dizziness, imbalance improve with XR; bitter taste with ODT, word-finding problems improve with dose-reduction; and insomnia with morning dosing. XR/ODT $5/mth at costplusdrugs.com. Lamotrigine is safest bipolar med in pregnancy. Although not FDA approved in children (except for seizures), it is a good choice in childhood bipolar as it PREVENTS mood episodes, but need to use very low (CBZ) starter for children (start 25 qod).

Best tolerated mood stabilizer, great for cyclothymic temperament, works slowly (4-8 weeks) in acute bipolar depression but mainly prevents new episodes in bipolar. Not ideal as monotherapy in bipolar I as it is weak against mania, but great for monotherapy in bipolar II.

EMR Text