Apokyn for Motor IMProvement of Morning AKinesia Trial (AM IMPAKT)

This Phase IV, Open-Label, Efficacy and Safety Study of APOKYN® is intended to assess the effect of APOKYN treatment in rapid and reliable improvement of motor symptoms in PD subjects suffering from delayed or unreliable onset of L-dopa action. The study will also include a sub-group of 8 subjects to evaluate their gastroparesis and assess their gastric empty with other measures to explore if APOKYN has any influence on gastric empty rather than just bypassing the stomach with a subcutaneous route of administration. The primary objective of this study is to assess the effect of APOKYN treatment in rapid and reliable improvement of motor symptoms in PD subjects suffering from delayed or unreliable onset of L-dopa action (defined below). APOKYN treatment will also be assessed in a sub-group of PD subjects suffering from gastroparesis and delayed onset of L-dopa action. Delayed or unreliable onset to L-dopa for the study population is defined as impaired motor function (tremor, bradykinesia, rigidity, and/or postural instability) persisting for a minimum of 45 minutes after taking a dose of L-dopa because of its delay in onset of action. The impaired motor function resulting from delay in L-dopa onset is referred to as "delayed ON" and when it occurs upon awakening is referred to as "morning akinesia." Main Study: This is a multicenter, multiple-treatment, open-label, outpatient study to evaluate the efficacy and safety of APOKYN in PD subjects with delayed onset of L dopa action. The study will have: * Screening - 1-5 days (Visit 1); * Baseline L-Dopa Period - 7 days, continuation of L dopa treatment; * Antiemetic Treatment Period - 3-days; initiation of trimethobenzamide 300 mg tid orally; * APOKYN Initiation/optimum dose identification Period (Visit 2)- variable, not more than 11 days; * APOKYN Treatment Period - 7 days, immediately upon identification of optimum dose; * Study Discharge (Visit 3)- within 2 days of completion of the APOKYN treatment period. Gastroparesis Sub-Study: A sub-group of subjects (n=8) from 1 study site that have symptoms of gastroparesis will be admitted to the clinic on 2 occasions to undergo gastroparesis procedures and assessments (once at the conclusion of the baseline L-dopa period and once at the conclusion of the APOKYN treatment period). Note, to do the second gastroparesis assessment, this sub-group of subjects will have an extension for one extra day beyond the designated 7 day APOKYN treatment period (i.e., it will be 8 days) in order to keep the 7 day diary recording outpatient scope of work the same as the rest of the subjects in the study. The second inpatient period will be also considered the end-of-study visit for this sub group.