Phenelzine is primarily used as an antidepressant in the treatment of major depressive disorder, particularly in cases where other antidepressants have not been effective. It belongs to the class of monoamine oxidase inhibitors (MAOIs), which work by increasing the levels of certain chemicals in the brain that help improve mood and reduce anxiety.

This medication is also sometimes prescribed for panic disorder and social anxiety disorder. Due to its mechanism of action, it requires careful dietary restrictions to avoid interactions with tyramine-rich foods, which can lead to dangerous increases in blood pressure.

Phenelzine is often considered when other treatment options have failed, as it can be highly effective but also carries a higher risk of side effects and interactions compared to newer antidepressants. Patients are typically monitored closely to manage any adverse effects and ensure the safe use of the medication.