If a patient is prescribed both Depakote and Lamictal, what adjustment is recommended for Lamictal?

• A. Decrease Lamictal dose by 50%
• B. Increase Lamictal dose by 50%
• C. No change to Lamictal dose
• D. Decrease Depakote dose by 50%

Answer: (A)

Valproate inhibits the metabolism of lamotrigine, increasing its blood levels. When both are used together, lamotrigine dosing must be reduced—typically by about 50%—and titration slowed to reduce the risk of toxicity, especially serious skin reactions like Stevens-Johnson syndrome. This adjustment helps prevent lamotrigine accumulation due to valproate’s effect on clearance. If valproate is later reduced or stopped, lamotrigine may require gradual up-titration with careful monitoring. Not adjusting would raise the risk of adverse effects, and increasing lamotrigine or decreasing valproate without proper oversight would not follow standard practice in this interaction.