Evaluation of the Long-term Safety, Tolerability, and Efficacy of Perampanel (E2007) as an Adjunctive Therapy in Levodopa Treated Parkinson's Disease Subjects With Motor Fluctuations

INCLUSION CRITERIA: Male or female subjects with idiopathic PD who have fulfilled the entry criteria to studies E2007-G000-309 or E2007-E044-213. Subjects must have completed the core efficacy study up to and including the final efficacy and follow up visits as applicable. Subjects with mild or moderate AEs thought to be related to Perampanel (E2007) can be entered into the study if the investigator considers it safe. EXCLUSION CRITERIA: 1. Show evidence of clinically significant disease (i.e., severe cardiovascular or pulmonary disease, bronchial asthma, endocrine disease, history of peptic ulcer disease, history of myocardial infarction with residual atrial nodal or ventricular arrhythmias) that, in the opinion of the investigator, could affect either the patient's safety or the conduct of the study. 2. Pregnant or lactating women. 3. Women of childbearing potential (WOCBP) unless infertile (including surgically sterile) or practicing effective contraception (e.g., intrauterine device \[IUD\] or barrier method plus hormonal method). These subjects must have a negative urine pregnancy test at Visit 1 or 2 as indicated by entry into the study. These subjects must also be willing to remain on their current form of contraception for the duration of the study. Postmenopausal women may be recruited but must be amenorrhoeic for at least 1 year to be considered of non-child bearing potential as determined by the investigator. 4. Subjects with a past (within the past 5 years) or present history of drug or alcohol abuse as per Diagnostic and Statistical Manual of Mental Disorders - Fourth Edition (DSM IV) criteria. 5. Antipsychotics are permitted as necessary. Subjects may be taking anti-depressant medication, however the dose must be stable for 4 weeks prior to their first study visit (the visit at which the inclusion and exclusion criteria are done with the patient). 6. Subjects with a past (within one year) or present history of major depression, suicidal ideation, or suicide attempts. 7. Subjects with unstable abnormalities of the hepatic, renal, cardiovascular, respiratory, gastrointestinal, haematological, endocrine, or metabolic systems that might complicate assessment of the tolerability of the study medication. 8. Subjects with significantly elevated liver enzymes (abnormal bilirubin or serum transaminase levels of more than 1.5 times the upper limit of the normal range). 9. Subjects with current or prior treatment (within 4 weeks prior to the Screening Visit) with medication known to induce the enzyme CYP3A4. 10. Clinically significant ECG abnormality, and/or prolonged QTc (defined as QTc ≥ 450 msec). 11. Current or prior treatment (within 4 weeks prior to entry visit) with tolcapone, methyldopa, budipine, or reserpine. 12. Subjects with previous stereotactic surgery (e.g., pallidotomy) for PD or with planned stereotactic surgery during the study period 13. Subjects receiving or with planned (next 12 months) deep brain stimulation. 14. Subjects with conditions affecting the peripheral or central sensory system unless related to PD (such as mild sensory or pain syndromes limited to OFF periods) that could interfere with the evaluation of any such symptoms caused by the study medication. 15. Subjects have received an investigational product (other than E2007 or entacapone 200 mg) within 4 weeks prior to Screening 16. Any condition that could, in the opinion of the investigator, place the subject at increased risk or is likely to prevent completion of the study. 17. Subjects with any condition that would make the subject, in the opinion of the investigator, unsuitable for the study. 18. Patients on pergolide or cabergoline.