Parkinson's Disease Isradipine Safety Study

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. Hypothesis 1: Patients with PD will be able to tolerate isradipine across the FDA recommended dose range. We expect 10% attrition due to hypotensive effect of the agent. Hypothesis 2: Patients with PD and concomitant stable hypertension will be able to tolerate isradipine provided that the dose of the concomitant antihypertensive agent is adjusted based on the blood pressure reading.

Isradipine safety profile Isradipine, FDA approved for treatment of hypertension since 1990, has a well established data on its efficacy and safety in the hypertensive population (see package insert, Appendix 3). The side effect profile of isradipine is related to the primary mechanism of action of the agent as a vasodilator of the vascular smooth muscles and myocardium, and includes hypotension, bradycardia, weakness, and syncope. As per package insert, the most common adverse effects are headache (13.7% with active treatment versus 14% placebo), dizziness (7.3 vs 4.4) and peripheral edema as reflection of the vasodilatory effect which is dose dependent with incidence of about 3.5% at 5 mg, 8.7% at 10 mg and 8.5% at 20 mg. Of note the incidence of edema is substantially lower compared to CR preparation (9:13:36% for the respective doses). The other side effects include angina, asthenia, flushing, heart failure, and palpitations. According to the package insert, the adverse effects are usually not serious, dose dependent, and respond well to dose reduction or discontinuation of therapy. Isradipine has no effect on atrioventricular or sinoatrial conduction. The only absolute contraindications for isradipine are hypersensitivity to DHP compounds and hypotension defined as systolic blood pressure below 90 mm Hg. Until our studies, isradipine has not been tested in the PD population.