Istradefylline (Nourianz®) is an adenosine A2A receptor antagonist used as an add-on therapy to levodopa/carbidopa in Parkinson’s disease. It helps reduce “off” episodes by modulating brain signaling pathways involved in motor control, offering a non-dopaminergic approach. Clinical studies show modest improvements in daily “on” time without troublesome dyskinesias. Common side effects include dyskinesia, hallucinations, dizziness, constipation, and insomnia. While not a first-line therapy, istradefylline provides an additional option for patients whose symptoms are not fully controlled with standard dopaminergic drugs.