List of products in the National Drug Code with proprietary name . This medication is used to treat movement disorders caused by Parkinson's disease. It does not cure Parkinson's disease, but it may improve shakiness (tremor), muscle stiffness, loss of normal movement as your dose of other Parkinson's medication wears off (end-of-dose failure), and sudden switching between normal movement and stiffness ("on-off" problems). It may improve your range of motion and ability to walk, dress, and exercise. Selegiline is usually used in combination with other medicines (e.g., levodopa, carbidopa). Selegiline is an enzyme blocker (MAO inhibitor) that works by slowing the breakdown of certain natural substances in the brain (neurotransmitters such as dopamine, norepinephrine, and serotonin).