Drug interactions
Lamotrigine + Valproic acid
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Overview
Valproate markedly increases lamotrigine exposure and risk of serious rash (including SJS/TEN) via inhibition of lamotrigine metabolism.
Mechanism of action
Pharmacokinetic: Valproate inhibits UGT-mediated glucuronidation of lamotrigine (notably UGT1A4), raising lamotrigine concentrations; pharmacodynamic: higher lamotrigine levels increase rash/CNS toxicity risk.
Clinical management
Use reduced lamotrigine starting and maintenance doses when combined with valproate; titrate slowly; avoid rapid dose escalation; educate about rash; discontinue lamotrigine at first sign of significant rash unless clearly non–drug related.
Drug reference
References
- Lamictal (lamotrigine) US Prescribing Information — FDA Label
- Depakote (divalproex sodium/valproic acid) US Prescribing Information — FDA Label
- Lamotrigine: Drug information — Lexicomp
Frequently asked questions
Can I take Lamotrigine with Valproic acid?
The interaction is rated: Major. Valproate markedly increases lamotrigine exposure and risk of serious rash (including SJS/TEN) via inhibition of lamotrigine metabolism.
How serious is the interaction between Lamotrigine and Valproic acid?
The interaction is rated: Major. Evidence level: High.
How is the interaction between Lamotrigine and Valproic acid managed?
Use reduced lamotrigine starting and maintenance doses when combined with valproate; titrate slowly; avoid rapid dose escalation; educate about rash; discontinue lamotrigine at first sign of significant rash unless clearly non–drug related.
Why do Lamotrigine and Valproic acid interact?
Pharmacokinetic: Valproate inhibits UGT-mediated glucuronidation of lamotrigine (notably UGT1A4), raising lamotrigine concentrations; pharmacodynamic: higher lamotrigine levels increase rash/CNS toxicity risk.
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