Selegiline, bettern known as Deprenyl, is an MAO-B Inhibitor in small quantities (under 25 mg) and also inhibits MAO-A in larger quantities. It was the first selective inhibitor of MAO-B. Selegiline is marketed as a Parkinson's disease cure. Other reported positive effects include cognitive enhancement, increased libido in men, and reports of life-span extension.

Effects are described as stimulating and a little similar to cocaine. Tolerance builds relatively quickly. The FDA approved a Selegine transdermal patch (Emsam) for use as an antidepressant in February, 2006.