American Board of Psychiatry and Neurology (ABPN) Practice Exam 2026 - Free ABPN Practice Questions and Study Guide

The interaction between valproic acid and lamotrigine is clinically significant, as valproic acid is known to inhibit the metabolism of lamotrigine. When these two medications are administered together, valproic acid increases the levels of lamotrigine in the body. This occurs because valproic acid competes with lamotrigine for the same metabolic pathways, primarily involving the UDP-glucuronosyltransferase enzymes that are responsible for the glucuronidation process.

As a result, the risk of side effects related to elevated levels of lamotrigine, including serious skin rashes and potential toxicity, is heightened, necessitating careful monitoring and possible dosage adjustments for lamotrigine when it is used in conjunction with valproic acid. This interaction highlights the importance of pharmacokinetic knowledge in clinical practice to ensure patient safety and therapeutic efficacy when combining antiepileptic drugs.

The other options provided do not describe clinically recognized interactions between these drugs. Lamotrigine is not known to increase valproic acid levels, and there is no significant evidence that carbamazepine affects lithium levels in a direct manner. Therefore, the primary and correct understanding lies in the impact of valproic acid on