Selegiline, also known by the brand names Eldepryl and Emsam among others, is a medication primarily used in the treatment of Parkinson’s disease and major depressive disorder (MDD). It belongs to the class of drugs called monoamine oxidase inhibitors (MAOIs), which work by inhibiting the activity of the enzyme monoamine oxidase. This enzyme is responsible for breaking down neurotransmitters such as dopamine, serotonin, and norepinephrine in the brain.