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

Clozapine is indeed a substrate of the cytochrome P450 enzyme CYP 1A2. This enzyme is important in the metabolism of various drugs, including those utilized in psychiatric treatment.

Carbamazepine is an inducer of several CYP enzymes, particularly CYP 3A4 and CYP 1A2. Drugs that are substrates of these enzymes may have their metabolism increased when carbamazepine is initiated, leading to lower plasma levels and reduced efficacy. However, clozapine is somewhat unique because, while it is a substrate for CYP 1A2, its metabolism is not significantly affected by carbamazepine. This is due to the fact that clozapine has a wide therapeutic range and its levels are primarily influenced by genetic factors and other drug interactions less than by carbamazepine.

In contrast, haloperidol, olanzapine, and risperidone are substrates of CYP 2D6 and/or CYP 3A4 and can have their plasma concentrations affected by carbamazepine. Understanding the influence of drug metabolism on psychotropic treatment is essential for clinicians in ensuring therapeutic effectiveness and preventing adverse effects.