American Board of Psychiatry and Neurology (ABPN) Practice Exam 2025 - Free ABPN Practice Questions and Study Guide

Phenelzine is the choice that is least likely to worsen extrapyramidal symptoms in individuals with Parkinson's disease. As a non-selective monoamine oxidase inhibitor (MAOI), phenelzine primarily affects the neurotransmitters serotonin and norepinephrine, rather than directly interfering with dopamine pathways. This is particularly important for patients with Parkinson's, where the management of dopamine levels is critical.

In contrast, other options such as amoxapine, perphenazine, and thorazine are antipsychotic agents known to have dopaminergic antagonist properties. These medications can block dopamine receptors, particularly in the nigrostriatal pathway, thereby exacerbating the motor symptoms associated with Parkinson's disease, such as tremors and rigidity. Clinicians often avoid these medications in treating psychiatric conditions for patients already diagnosed with Parkinson's to mitigate the risk of worsening extrapyramidal symptoms.

Thus, phenelzine's unique mechanism of action makes it a safer option for patients with Parkinson's disease, as it does not contribute to worsening these motor symptoms.