Lamotrigine and Valproic Acid: Drug Interaction Guide
Quick answer: This is a major interaction — avoid combining Lamotrigine and Valproic Acid unless specifically directed by your doctor.
How Lamotrigine interacts with Valproic Acid
Valproate inhibits UGT1A4-mediated glucuronidation of lamotrigine, doubling its half-life and plasma concentrations, increasing the risk of serious rash including Stevens-Johnson syndrome.
What you should do
When adding lamotrigine to valproate, halve the standard lamotrigine titration schedule (e.g., 25 mg every other day initially) and titrate very slowly.
Key facts
Severity
Major — avoid combination
Mechanism
Valproate inhibits UGT1A4-mediated glucuronidation of lamotrigine, doubling its half-life and plasma concentrations, inc...
Action
When adding lamotrigine to valproate, halve the standard lamotrigine titration schedule (e.g., 25 mg every other day ini...
Frequently asked questions
Can I take Lamotrigine and Valproic Acid together?
No — this combination should generally be avoided. When adding lamotrigine to valproate, halve the standard lamotrigine titration schedule (e.g., 25 mg every other day initially) and titrate very slowly.
What is the severity of this interaction?
The interaction between Lamotrigine and Valproic Acid is classified as Major — avoid combination. Valproate inhibits UGT1A4-mediated glucuronidation of lamotrigine, doubling its half-life and plasma concentrations, increasing the risk of serious rash including Stevens-Johnson syndrome.
What should I do if I'm prescribed both?
When adding lamotrigine to valproate, halve the standard lamotrigine titration schedule (e.g., 25 mg every other day initially) and titrate very slowly. Always consult your prescribing clinician — do not stop or change medications without medical guidance.
Last reviewed: by iMedic Medical Editorial Team. Our editorial process.