Patients with a clinically significant illness of any organ system, including hepatic, renal, pancreatic, cardiovascular, endrocrinologic, gastrointestinal, respiratory, and neurologic system (except for those with Parkinson's disease) who may require a change in the treatment of that illness during the trial, or that may compromise the safety of the patient volunteer during the trial, or that may affect the ability of the volunteer to complete the trial will be excluded.