Patient description: A 57-year old farmer was diagnosed with Parkinson's disease a year ago. He experiences slowness of movement and tremors. His past medical history is significant for hypertension and hypercholesterolemia. He lives with his wife. They have three children. He used to be active with planting and taking care of their farm animals before his diagnosis. The patient complains of shaking and slow movement. He had difficulty entering through a door, as he was frozen and needed guidance to step in. His handwriting is getting smaller. He is on Levodopa and Trihexyphenidyl. He stated his medications help with shaking and slow movement. But he still has difficulty initiating movements, stiffness and slowness in general. He is an alert and cooperative man who doesn't have any signs of dementia. He doesn't smoke or use any illicit drugs.

Clinical trial eligibility criteria: eligible ages (years): 18.0-75.0,  Parkinson Disease Patient had Parkinson's Disease that meet the clinical diagnostic of the brain bank of the Parkinson's Disease Association of the United Kingdom. 2. Patient was Hoehn & Yahr stage ≤3 (excluding stage 0) ; 3. Patient was male or female aged 18 to 75 years; 4. Patient had a Mini Mental State Examination (MMSE) score of ≥25; 5. Patient had a Unified Parkinson's Disease Rating Scale (UPDRS) motor score (Part III) of ≥10 but ≤30 at Screening. 6. Patient who signed the informed consent form volunteered to participate in this clinical trial and could cooperate with the prescribed inspections  Patient had atypical Parkinson's syndrome(s) due to drugs (e.g., metoclopramide, flunarizine), metabolic neurogenetic disorders (e.g., Wilson's disease), encephalitis, cerebrovascular disease, or degenerative disease (e.g., progressive supranuclear palsy); 2. Patient had a history of pallidotomy, thalamotomy, deep brain stimulation, or fetal tissue transplant; 3. Patient had dementia, schizophrenia or hallucinations, or clinically significant depression; 4. Patient had a lifetime history of suicide attempt (including an active attempt, interrupted attempt, or aborted attempt), or presence of suicidal ideation in the past 6 months as indicated by a positive response ("Yes") to either Question 4 or Question 5 of the Columbia-Suicide Severity Rating Scale (C-SSRS) at Screening; 5. Patient had a history of orthostatic hypotension with a decrease of ≥20 mmHg in systolic blood pressure (SBP) or ≥10 mmHg in diastolic blood pressure when changing from the supine to the standing position and keeping in the standing position for 3 minutes; 6. Patient had received therapy with a dopamine (DA) agonist either concurrently or had done so within 28 days prior to the Screening; 7. Patient had received therapy with 1 of the following drugs either concurrently or within 28 days prior to Screening: monoamine oxidase B (MAO-B) inhibitors (e.g., pargyline, selegiline), DA releasing agents (e.g., amphetamine), reserpine, DA-antagonists (e.g., metoclopramide), neuroleptics, or other medications that may interact with DA function; 8. Patient was currently (at the time of Screening) receiving central nervous system active therapy (e.g., sedatives, hypnotics, antidepressants, anxiolytics), unless the dose had been stable for at least 28 days prior to Screening Visit and was likely to remain stable for the duration of the study; 9. Patient had a current diagnosis of epilepsy, had a history of seizures as an adult within 1 year prior to Screening, had a history of stroke or transient ischemic attack within 3 months prior to Screening; 10. Patient had a history of known intolerance/hypersensitivity to non-dopaminergic antiemetics, such as domperidone, ondansetron, tropisetron; 11. Patient had clinically significant liver dysfunction (which defined as total bilirubin above the upper limit of normal range, or alanine transferase (ALT) and / or aspartate transferase (AST) 2 times higher than the upper limit of normal range); 12. Patient had clinically significant renal insufficiency (serum creatinine >2.0 mg/dL [ >178 μmol/L]); 13. Patient had clinically significant cardiac insufficiency and/or had myocardial infarction in the past 12 months; 14. Patient had a history of allergic to any medication; 15. Heavy smoker, alcoholic, drug addict; 16. Female patients who were pregnant or were breastfeeding or were of childbearing potential without adequate contraception; male patients who cannot take adequate contraception during the study; 17. Patient who was inappropriate to participant in the study in the judgment of the Investigator