Istradefylline, sold under the brand name Nourianz, is a medication used as an add-on treatment to levodopa/carbidopa in adults with Parkinson's disease (PD) experiencing "off" episodes.

[2] Relatively common side effects include involuntary muscle movements (dyskinesia), constipation, hallucinations, dizziness and, much like its parent molecule caffeine, nausea and sleeplessness.

[5] Istradefylline is a selective antagonist at the adenosine A2A receptor (A2AR), but the precise mechanism by which it exerts its therapeutic effect in Parkinson's disease is unknown.

In all four studies, people treated with Nourianz experienced a statistically significant decrease from baseline in daily "off" time compared to patients receiving a placebo.

[12][13] Istradefylline shows pro-motivational effects in animals and has been found to reduce apathy, fatigue, and anhedonia in people with Parkinson's disease.