My husband has Parkinson s and is constipated regularly. His doctor recommended he take Miralax 2 x a day. And for the first month it worked well and often. This past week he has not had a bowel movement, and I am wondering if I should go to the next step of Magnesium Sulfate, and if so, can I give it to him in 2 or 3 doses during the day, instead of just one, which he will not take.