Lamotrigine and Valproate Interaction
Drug interaction information between Lamotrigine and Valproate.
Lamotrigine and Valproate have a documented minor interaction in FDA labeling.
FDA drug labeling documents a minor-severity interaction between Lamotrigine and Valproate. Major interactions are generally avoided, moderate ones may need monitoring or a dose adjustment, and minor ones are usually low-risk. This page shows the documented mechanism and guidance. Label-documented interactions are not a complete safety review, so always confirm your own medications with a pharmacist or doctor. Educational information, not medical advice.
How They Interact
Valproate slows down the process your body uses to get rid of lamotrigine, which causes the amount of lamotrigine in your blood to more than double.
What To Do
Your doctor will likely need to lower your lamotrigine dose to avoid side effects.
FDA Label Information
Valproate ↑ lamotrigine ? valproate Increased lamotrigine concentrations slightly more than 2-fold. There are conflicting study results regarding effect of lamotrigine on valproate concentrations: 1) a mean 25% decrease in valproate concentrations in healthy volunteers, 2) no change in valproate concentrations in controlled clinical trials in patients with epilepsy.
Lamotrigine Also Interacts With
- Dofetilide moderate
- Desmopressin moderate
- Carbamazepine minor
- Rifampin minor
- Phenytoin minor
Valproate Also Interacts With
- Ranitidine major
- Cimetidine major
- Clarithromycin moderate
- Lidocaine Topical moderate
- Risperidone moderate
Frequently Asked Questions
Can I take Lamotrigine and Valproate together?
This is a minor interaction. Your doctor will likely need to lower your lamotrigine dose to avoid side effects.
How serious is the interaction between Lamotrigine and Valproate?
This interaction is classified as "minor" severity by the FDA. Minor interactions are unlikely to cause significant problems but should still be mentioned to your healthcare provider.
Why do Lamotrigine and Valproate interact?
Valproate slows down the process your body uses to get rid of lamotrigine, which causes the amount of lamotrigine in your blood to more than double.
Understanding the Lamotrigine and Valproate Interaction
FDA-approved prescribing information for these two drugs flags their combination as a minor-severity interaction. Lamotrigine belongs to the Anticonvulsant class and Valproate belongs to the Anticonvulsant / Mood Stabilizer class - two categories that can collide when co-prescribed. The mechanism described in FDA labeling is: Valproate slows down the process your body uses to get rid of lamotrigine, which causes the amount of lamotrigine in your blood to more than double. Severity tiers matter: major flags generally advise avoidance, moderate flags often require monitoring or dose adjustment, and minor flags may only call for awareness.
Context around a specific patient determines real-world impact. Lamotrigine has 24 total documented interactions on file in this dataset, and Valproate has 41. Each additional medication compounds the interaction surface, which is why pharmacists run full-profile checks rather than evaluating one pair at a time. FDA-derived guidance for this pair is: Your doctor will likely need to lower your lamotrigine dose to avoid side effects. Timing of doses, renal and hepatic function, age, and other concurrent prescriptions all shape whether a labeled interaction matters clinically.
An interaction flag is not a verdict. A large share of labeled interactions are managed routinely in clinical practice, the fix may be as simple as spacing doses or adding a monitoring test. Others require the prescriber to choose a different medication entirely. This page surfaces FDA-sourced labeling and openFDA data for educational purposes only; it is not medical advice and cannot account for your full clinical picture. Never start, stop, or adjust either Lamotrigine or Valproate based on a web page, speak with your prescriber or pharmacist before making any change.
Sources: FDA Drug Labels (SPL) via openFDA (2026). This is for informational purposes only and is not medical advice. Always consult your healthcare provider about drug interactions.
Read our methodology - how this data is sourced, computed, and verified.