["parkinson's disease", 'levodopa induced dyskinesia (lid)']
['amantadine hcl er', 'placebo']

        Inclusion Criteria:

          -  Signed Institutional Review Board (IRB)/ Independent Ethics Committee (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.
      