In its pill form, selegiline is used to treat symptoms of Parkinson's disease. It is most often used as an adjunct to drugs such as levodopa (-DOPA), although it has been used off-label as a monotherapy. The rationale for adding selegiline to levodopa is to decrease the required dose of levodopa and thus reduce the motor complications of levodopa therapy. Selegiline delays the point when levodopa treatment becomes necessary from about 11 months to about 18 months after diagnosis. There is some evidence that selegiline acts as a neuroprotectant and reduces the rate of disease progression, though this is disputed.
Selegiline has also been used off-label as a palliative treatment for dementia in Alzheimer's disease.