Abstract: The invention described herein provides a fast dispersing oral solid dosage form containing monoamine oxidase B inhibitor (MAO-B inhibitor) as the active ingredient, and method of treating disease therewith, such as Parkinson's disease. In one embodiment, the monoamine oxidase B inhibitor selegiline or its analogue can be the sole active ingredient in the composition administered. The dosage form composition is formulated to promote absorption through the buccal, sublingual, pharyngeal and/or esophageal mucous membrane tissue, such that at least 5% of the active ingredient is absorbed within one minute of placement in the oral cavity, as determined by a buccal absorption test. Monoamine oxidase B inhibitor compounds administered in accordance with the invention decrease the amount of undesirable metabolites associated with first pass effect of selegiline, for example, such as amphetamine and methamphetamine.