Tranylcypromine HCl is primarily used as an antidepressant in the treatment of major depressive disorder, particularly in cases where other treatments have been ineffective. It functions as a monoamine oxidase inhibitor (MAOI), which helps increase the levels of certain chemicals in the brain that are responsible for mood regulation. This makes it effective for patients with atypical or treatment-resistant depression. Additionally, it has been explored for its potential use in managing anxiety disorders and certain types of chronic pain. Due to its mechanism of action, it requires careful dietary restrictions to avoid adverse interactions with tyramine-rich foods, which can lead to hypertensive crises. Its application is typically reserved for patients under close medical supervision.