American Board of Psychiatry and Neurology (ABPN) Exam 2025 – 400 Free Practice Questions to Pass the Exam

The correct answer is that tobacco is not an inhibitor of cytochrome P450 (CYP) 1A2. In fact, tobacco smoke can actually induce this enzyme rather than inhibit it, leading to increased metabolism of drugs that are substrates of CYP 1A2. The other options—amiodarone, cimetidine, and fluvoxamine—are known inhibitors of CYP 1A2.

Amiodarone is an antiarrhythmic medication that can alter liver enzyme activity, including inhibition of CYP 1A2. Cimetidine, a histamine H2 receptor antagonist, is well-documented to inhibit several cytochrome P450 enzymes, including CYP 1A2. Fluvoxamine, an SSRI often used in the treatment of obsessive-compulsive disorder, is also a potent inhibitor of CYP 1A2, which can lead to drug-drug interactions when co-administered with medications that are metabolized by this pathway.

Understanding the roles of various substances in affecting the cytochrome P450 system is crucial for anticipating potential drug interactions and managing patient pharmacotherapy effectively.