NutriStack
Lamotrigine and Valproic Acid, a caution.
Valproic acid inhibits the glucuronidation of lamotrigine, approximately doubling lamotrigine levels. This increases the risk of serious skin reactions including Stevens-Johnson syndrome, especially during lamotrigine titration.
One pair, every claim cited. The two substances, the type, the mechanism, the recommendation, and the primary literature.
Same shape as the other 1,729 pairs in the public database.
From the interaction database
What the row says.
Every entry follows the same shape: what is happening, the mechanism, the recommendation, and the primary literature.
At a glance
- Substances
- Lamotrigine and Valproic Acid
- Pair type
- Caution
- Evidence (highest tier)
- Strong
- Source citations
- 1 source
- Stack Score effect
- −5 to your Stack Score (per scored caution row).
- Scope
- Supplement × Prescription
- Last verified
- May 30, 2026
Caution · Strong evidence
Caution
What is happening. Valproic acid inhibits the glucuronidation of lamotrigine, approximately doubling lamotrigine levels. This increases the risk of serious skin reactions including Stevens-Johnson syndrome, especially during lamotrigine titration.
Mechanism. Valproic acid inhibits UGT1A4-mediated glucuronidation of lamotrigine, reducing lamotrigine clearance by approximately 50% and doubling its half-life from 25 to 48-70 hours.
Recommendation. When used together, lamotrigine dose must be reduced by 50% and titrated very slowly. Standard lamotrigine titration schedules have specific reduced-dose protocols for valproate co-administration.
Sources (1)
Stack Score
How this pair moves the number.
Effect on the composite score
If both Lamotrigine and Valproic Acid are in the same stack, this pair applies −5 to your Stack Score (per scored caution row).
The full algorithm, the clamping rules, and four worked stacks are documented at /methodology/stack-score.
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