Ya she a parkinson patient nd is on regular doses of laxatives. She has no pain in stomach nd prety ok othrwise. What dose of miralax (polyethylene glycol) u suggest?

17 g daily. Start with 17 g daily and titrate dose to effect. Would not go above 34 g twice daily without following with a gastroenterologist. It is usually helpful to take bisacodyl 10 mg once or twice daily in addition to MiraLAX (polyethylene glycol) in a patient with Parkinson's disease.
For constipation. try Senna, it is much safer than Miralax (polyethylene glycol). Senna is a natural plant product. Start by taking 2 tablets at bedtime, if you do not have a comfortable bowel movement (BM) the next day, take 4 tablets the next night. You can continue to increase the dose by 2 tablets every night until it works. Once you find the dose that works for you, taking that same dose every night should keep you regular.