Efficacy of adenosine A2A receptor antagonist istradefylline as augmentation for Parkinson's disease: a meta-analysis of randomized controlled trials.

Adenosine A2A receptor antagonist istradefylline has been approved this year for manufacturing and marketing in Japan. We, therefore, did this meta-analysis to systematically assess the efficacy and safety of istradefylline as augmentation to levodopa in patients with Parkinson's disease (PD). We systematically review the relative randomized controlled trials (RCTs) up to March 2014, which compared istradefylline to placebo for the short course of treatment for PD in adults. The primary outcome was daily OFF time and secondary outcome was UPDRS Part III score (on state). Data were obtained from seven RCTs, including 2205 patients. Compared to placebo on primary and secondary outcome, istradefylline group both showed significant reductions (WMD -0.60, p = 0.0001; WMD -1.07, p = 0.002). Subgroup analysis suggested that istradefylline 20, 40, and 60 mg/day in both group showed significant reductions on the two outcomes. Based on these results, Istradefylline could be an efficacy and safety augmentation drug added on to levodopa or other existing anti-Parkinsonian therapies. Limited by the number of studies, future large-scale studies are needed to verify these results, assess the long-term effect of istradefylline and the effect of istradefylline as monotherapy, and find the most effective dose of istradefylline.