HALF-LIFE: 25-33 hours
>With valproic acid: 48-70 hours
>With Carbamazepine: 13-14 hours
STARTING DOSE: 25mg PO daily
TARGET DOSING RANGE: 50mg-200mg per day
BEST TIME TO DOSE: Any (causes insomnia in some patients)
HOW TO DOSE:
If dosing without valproic acid:
>Initial 25mg PO Daily for two weeks
>Increase to 25mg PO BID for two weeks
>Increase to 50mg PO BID for two weeks
>If tolerated, can consolidate to once daily dosing
>Max dose without valproate typically 200mg per day
If dosing with valproic acid:
>Initial 25mg PO every other day for two weeks
>Increase to 25mg PO daily for two weeks then 50mg PO daily
>Max dose with valproate typically 100mg per day
*RESTART TITRATION IF STOPPED/MISSED FOR >5 HALF LIVES*
PREGNANCY: Minimal data on safety in humans. Must weigh risk of discontinuing vs risk of teratogenicity (which is low)
BREASTFEEDING: Minimal data on safety in humans. Recommend bottle/formula feeding
1) Bipolar Disorder (maintenance/preventing mood episodes)
2) Seizures in adults and children
Lamotrigine shows prophylactic and antidepressant properties, but is no better than placebo in treating mania
Lamotrigine has been shown to reduce glutamate release and modulate reuptake of monoamines including serotonin and dopamine
Lamotrigine has been shown to increase the time between both depressive and manic episodes
May be a good add-on medication with lithium for bipolar depression
Mostly case reports and open labeled trials support lamotrigine in rapid cycling bipolar disorder, bipolar depression, and mixed episodes but RCTs have not consistently demonstrated efficacy for these conditions
Lamotrigine carries a risk of both benign rash and Steven Johnson’s Syndrome/TEN
Rash associated with rapid dose escalation
Reduce dose and slow titration if benign rash develops
Interaction between valproic acid and lamotrigine: Valproic acid inhibits lamotrigine metabolism; dose of lamotrigine must be decreased by half the normal dose when given in combination with valproic acid
Many hormonal contraceptives decrease lamotrigine levels – Caution during contraceptive-free “pill-free” periods as lamotrigine levels may rise substantially. Conversely, lamotrigine may decrease levels of hormonal contraceptives
Carbamazepine decreases lamotrigine levels
If lamotrigine stopped/missed for >5 half-lives then strongly consider restarting titration
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