Selegiline is a monoamine oxidase type B (MAO-B) inhibitor used primarily as an adjunct therapy in the treatment of Parkinson's disease. It helps to conserve the amount of dopamine available in the brain by preventing its breakdown, thereby prolonging the effects of levodopa.

Ropinirole is a dopamine agonist used in the treatment of Parkinson's disease and Restless Legs Syndrome (RLS). It acts directly on dopamine receptors in the brain, mimicking the effects of dopamine to help improve motor function and reduce the urge to move the legs.

Levodopa/Carbidopa is the most effective and commonly prescribed medication for managing the symptoms of Parkinson's disease. Levodopa is converted into dopamine in the brain to replenish depleted stores, while carbidopa prevents the premature breakdown of levodopa outside the brain, reducing side effects and increasing efficacy.