ABSTRACT
Background: Istradefylline is a selective adenosine A2A receptor antagonist approved for Parkinson’s disease (PD) patients with wearing-off symptoms. The Japanese phase III trial showed that 20 mg of orally administrated istradefylline decreased the Off-time. However, istradefylline showed prominent effects in some patients and no benefits in others. We examined the differences in characteristics between responders and non-responders who received 8 weeks of 20 mg/day istradefylline. Methods: Thirty-one patients were enrolled (age, 65.4 [SD 10.4] years; disease duration, 10.4 [SD 6.1] years; daily levodopa dosage, 553.2 [SD 228.7] mg; frequency of levodopa consumption, 4.7 [SD 1.5] times; levodopa equivalent dose, 811.2 [SD 307.5] mg). Results: There were significant differences (p < 0.05) in sex (male/female: 5/16, 6/4), age (62.9 (SD 10.4), 70.6 (SD 8.0) years), age at onset (51.9 (SD 12.3), 61.5 (SD 10.5) years old), age at dyskinesia onset (57.9 (SD 8.8), 67.6 (SD 7.2), and Epworth sleepiness scale scores (4.5 (SD 2.7), 11.2 (SD 6.7), p < 0.01) for the responders and non-responders, respectively. There were no differences in disease duration, On-time, Off-time, Unified Parkinson’s disease Rating scale scores, daily levodopa dose, levodopa equivalent dose, cumulative levodopa dose, or coffee intake. Conclusions: Younger or female patients who are not excessively sleepy during daytime are better candidates for the istradefylline therapy.