Orally Administered ENT-01 for Parkinson's Disease-Related Constipation Follow-on Safety "Roll-over" Study (Rollover)

The study will be conducted on an out-patient or in-patient basis with visits performed at the screening visit, at 6 and 12 weeks, and at the end of the 6th week of the wash-out period (end of study). The dose escalation period will last up to 20 days, the fixed dose period will last 12 weeks, and the wash-out period will last 6 weeks. Subjects will begin dosing at the same dose level they were stratified to in the ENT-01-030 randomized study (i.e., starting at either 3 tablets or 6 tablets,) and escalate up to a pro-kinetic dose or a maximum dose of 250mg.