Efficacy and Safety of Amantadine Hydrochloride (HCl) ER Tablets to Treat Parkinson's Disease Patients With LID.

• Signed Investigational Review Board/Independent Ethics Review Committee (IRB/IEC) informed consent form.,
• Idiopathic Parkinson's disease per the United Kingdom (UK) Parkinson's Disease Society Brain Bank criteria.
• Male or female 30 to 85 years old.
• Levodopa induced, predictable peak-effect dyskinesia considered problematic and/or disabling.
• Screening serum creatinine level within normal range
• On stable doses of all oral anti-Parkinson's medication, including any levodopa preparation, for 30 days and be willing to remain on the same doses throughout the trial.
• The subject/caregiver must demonstrate the ability to complete an accurate home diary based on training and evaluation during the screening period.

Exclusion Criteria:

• Secondary parkinsonian syndrome, such as vascular, postinflammatory,drug-induced, neoplastic and post-traumatic parkinsonism or any atypical parkinsonian syndrome (e.g., Progressive Supranuclear Palsy, Multi-System Atrophy, etc.);
• Use of amantadine within 14 days before study start, or previously had an adverse event to amantadine
• Currently taking neuroleptics and atypical antipsychotic agents, acetylcholinesterase inhibitors, apomorphine, rimantadine, memantine and dextromethorphan and quinidine if used in combination for treating dyskinesia.
• History of neurosurgical intervention for treating Parkinson's s disease (i.e. pallidotomy or implanted with a deep brain stimulator).
• Any medical condition or past medical history that would increase the risk of exposure to Amantadine HCl Extended Release Tablets or interfere with safety and efficacy evaluations.
• History of cancer within 5 years of screening with following exceptions: adequately treated non-melanomatous skin cancers, localized bladder cancer, non-metastatic prostate cancer or in situ cervical cancer.
• History or current diagnosis of schizophrenia or bipolar disorder;
• Inadequately treated Major Depressive Disorder. Subjects on stable doses of selective serotonin reuptake inhibitors (SSRIs) or serotonin-norepinephrine reuptake inhibitors (SNRIs) are eligible for the study.
• Is at imminent risk of suicide or had a suicide attempt within 6 months of screening
• History or current diagnosis of Impulse Control Disorder
• Calculated plasma creatinine clearance of \<60 mL/min at screening
• History of or currently has any of the following clinically significant conditions, cardiovascular, respiratory, renal, hepatic, or gastrointestinal disease
• Any clinically significant vital sign, ECG, or laboratory abnormalities:
• A positive test for HIV antibody or history of HIV; hepatitis B surface antigen unless the positive test followed a recent (\<28 days) vaccination for hepatitis B; hepatitis C antibody.
• A positive urine drug test.
• Pregnant or breastfeeding at screening or has a positive pregnancy test
• If a sexually active female, is not surgically sterile or at least 2 years post-menopausal, or does not agree to utilize an effective method of contraception from the screening visit to at least 4 weeks after the completion of study treatment.
• History of alcohol or narcotic substance abuse ≤1 year before screening.
• Has dementia or another psychiatric illness that prevents provision of informed consent.
• Has a known hypersensitivity to the study treatment(s), based on known allergies to drugs of the same class including rimantadine HCl and memantine HCl.
• Has participated in other studies involving investigational drugs or surgeries within the last 30 days or investigational biologics within the last 6 months prior to screening.
• Plans to undergo major elective surgery during the course of the study.
• Received administration of Live Attenuated Influenza Vaccine (LAIV) within 2 weeks.
• Cognitive impairment, as evidenced by a score \<26 on the Montreal Cognitive Assessment (MoCA) at the screening visit.