Think Twice Before Pushing Lamotrigine Higher

Dose escalation beyond 200 mg/day in bipolar depression lacks evidence and delays better options

SOURCE: Bernardoff L and Blay M, J Affect Disord 2026;407:121823

SOURCE TYPE: Correspondence (narrative review with meta-analytic evidence synthesis)

FUNDING: Independent

Dosing Limits

The authors review findings on lamotrigine dosing in bipolar depression:

• Evidence is stronger for prevention of depression than treatment of acute depression
• My own take: Most trials in acute depression only lasted 5 weeks, which is barely enough to titrate lamotrigine, but it does work (slowly) in trials lasting 4-12 weeks
• Although 200 mg worked better than the barely effective 50 mg in a meta-analysis, there was no evidence that going beyond 200 mg added efficacy. In a head-to-head comparison, 400 mg was not more effective than 200 mg.

Serum Levels: A Minimum May Be Necessary

Here we have conflicting evidence:

• There was no relationship between serum level and response in a retrospective therapeutic drug monitoring dataset. In that study, the mean lamotrigine concentration was 3.3 ± 2.6 μg/mL, and 61% were below the “effective threshold” which is established for epilepsy, not bipolar (3-14 μg/mL).
• However, two studies found greater response above 3.25 μg/mL, but an analysis of all the data found serum levels inconsistent and no evidence that responses rise with serum levels produce

When Higher May Be Better

Here’s where higher doses (300-400 mg) may be more effective due to pharmacokinetics:

1. Enzyme-inducing medications are on board: Some anticonvulsants (carbamazepine, phenytoin, phenobarbital, primidone), estrogen-containing birth control, and a few HIV meds.
2. Rapid metabolizers at glucuronidation enzymes: This is rare: mainly UGT1A4, to a lesser extent UGT2B7 and UGT2B1.
3. Third trimester of pregnancy.

My take: Genetics is only a rough guide to serum level, so check the level if your patient has UGT1A4 variants.

The Risk of Going Higher

• The authors argue that raising the dose to 400 mg to treat depression wastes valuable time, allowing depression to set in while effective strategies are missed.
• My take: Cognitive side effects and sleep disruption worsen on higher doses, particularly in the elderly.

— Chris Aiken, MD
Director, Psych Partners
Editor in Chief, Carlat Psychiatry Report

What’s Your Take? Share in Comments

1. What are you seeing at low vs high doses of lamotrigine?