Safety and Efficacy Study of SYN115 in Parkinson's Patients Using Levodopa to Treat End of Dose Wearing Off

Inclusion Criteria: * Meet Parkinson's Disease (PD) diagnosis consistent with UK PD diagnostic criteria * Meet Hoehn and Yahr PD stage * Good response to levodopa * Stable regimen of anti-parkinson medications * Are able to complete a Parkinson's disease diary * If of childbearing potential(male and female), use an acceptable method of birth control * Able and willing to sign an IRB/IEC approved informed consent * Able and willing to understand study requirements, follow study instructions, attend all visits and undergo all planned tests. Exclusion Criteria: * Secondary or atypical Parkinson's * Neurosurgical intervention for Parkinson's disease * Treatment with apomorphine * Treatment with anti-psychotic drugs * Other abnormal findings on physical or neuro exam or history that in the opinion of the investigator would make subject unsuitable for the study or prejudice safety and efficacy evaluation * MMSE less than 26 * Subjects with untreated or uncontrolled current episode of major depression * Receipt of any anti-psychotic drugs greater than 1 month in the past 5 years or any exposure in past year (except for quetiapine at doses \<100mg per day) * Women pregnant or lactating * History of hepatitis, cholangitis * Untreated or uncontrolled hypothyroidism or hyperthyroidism * Drops in blood pressure requiring medication to maintain blood pressure * Any clinically significant out of range laboratory evaluations * Known sensitivity to the study medication or its components * Suicide ideation or type 4 or type 5 on the Columbia suicide severity rating scale * Finding of malignant melanoma on full body skin exam * Impulse disorder conditions