Drug interactions
Divalproex + Lamotrigine
Severity: Major
Divalproex and Lamotrigine: major interaction.
Last updated
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.
Summary
Valproate roughly doubles lamotrigine exposure by slowing its elimination. This increases the risk of toxicity and of serious skin reactions, including Stevens-Johnson syndrome, particularly if lamotrigine is titrated at the usual rate.
What this interaction means in plain words
Divalproex and Lamotrigine can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Why it happens
Valproate inhibits UGT-mediated glucuronidation of lamotrigine, prolonging its half-life.
What to do
Use the reduced lamotrigine starting dose and slower titration schedule from the labeling when adding it to valproate. Halve the lamotrigine dose when valproate is added and counsel patients to report any rash immediately.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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Other interactions of Lamotrigine
Frequently asked questions
Can I take Divalproex with Lamotrigine?
MediHelp rates the interaction as major. Divalproex and Lamotrigine can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Valproate roughly doubles lamotrigine exposure by slowing its elimination. This increases the risk of toxicity and of serious skin reactions, including Stevens-Johnson syndrome, particularly if lamotrigine is titrated at the usual rate.
How serious is the interaction between Divalproex and Lamotrigine?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Use the reduced lamotrigine starting dose and slower titration schedule from the labeling when adding it to valproate. Halve the lamotrigine dose when valproate is added and counsel patients to report any rash immediately.
What other medicines interact with Lamotrigine?
MediHelp also lists interactions of Lamotrigine with, for example, Desogestrel-ethinyl estradiol, Dofetilide, Ethinyl estradiol-drospirenone. The full list is on the Lamotrigine page.
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