Istradefylline tablets have received FDA as an add-on treatment to levodopa and carbidopa for adults with Parkinson disease during 鈥渙ff鈥� episodes when symptoms increase because medications aren鈥檛 working well. The drug has been marketed in Japan since 2013 as adjunctive therapy for Parkinson disease.

Marketed as Nourianz, is a selective adenosine A_2A receptor antagonist that boosts dopamine signaling, which is deficient in the brain when patients have Parkinson disease. The drug鈥檚 efficacy was shown in four 12-week clinical trials involving 1143 patients. In each study, participants who received istradefylline had a statistically significant decrease in daily off time compared with those who received a placebo. The most common adverse reactions were dyskinesia, dizziness, constipation, nausea, hallucination, and insomnia.