Which of the following MAO inhibitors is used as an antidepressant?

Selegiline is a monoamine oxidase inhibitor (MAOI) that is used as an antidepressant, particularly in the treatment of major depressive disorder. MAO inhibitors like selegiline work by preventing the breakdown of neurotransmitters such as serotonin, norepinephrine, and dopamine, which are often imbalanced in individuals with depression. By inhibiting the monoamine oxidase enzyme, selegiline increases the availability of these neurotransmitters, helping to alleviate depressive symptoms.

Selegiline can be administered in various forms, including transdermal patches, which provide a steady release and reduce some common dietary restrictions associated with oral MAO inhibitors. It is considered particularly effective in cases of treatment-resistant depression and may also be useful for patients with bipolar disorder in a depressive phase.

The other options provided represent different classes of antidepressants. Fluoxetine is a selective serotonin reuptake inhibitor (SSRI), venlafaxine is a serotonin-norepinephrine reuptake inhibitor (SNRI), and amitriptyline is a tricyclic antidepressant. While all of these medications are employed in treating depression, selegiline is the specific MAO inhibitor among the choices listed.