NAPLEX (North American Pharmacist Licensure Examination) Practice Exam

When lamotrigine is taken with valproate, it significantly increases the levels of lamotrigine in the body. Valproate inhibits the metabolism of lamotrigine, leading to higher concentrations of lamotrigine. This increase in lamotrigine levels can potentially raise the risk of severe skin reactions such as Stevens-Johnson Syndrome (SJS) or Toxic Epidermal Necrolysis (TEN). Therefore, it is essential to monitor lamotrigine levels closely when it is co-administered with valproate.

Options A and B are incorrect because when lamotrigine is taken with valproate, there is indeed a change in the levels of lamotrigine, and they do not decrease. Option D is incorrect because although the levels increase, the more significant concern lies with the risk of severe skin reactions such as SJS/TEN rather than liver failure when lamotrigine is combined with valproate.