The objective of this study is to establish the safety and tolerability of isradipine, sustained release preparation in patients with PD. This study is a logical continuation of the project that is being completed now and is conducted in preparation to NIH submission of the pivotal study on the efficacy of this agent for neuroprotection in PD. This study is conducted in parallel with Dr. Surmeier's work on further development of the preclinical data. The focus of his work now is to establishing the correlation between the dose that demonstrated neuroprotective effect in animal model and the dose used for clinical practice.