So I work at an assisted living facility where part of my job description is to administer medications in the morning. There is one resident who takes Miralax (polyethylene glycol) mixed in with water once per day for constipation. This is a doctor's order, so he must get it every day. The problem is that the resident has dysphagia, and all liquids must be thickened before he drinks them. We use a product called "Thick-It" which is combination of modified food starch and maltodextrin, according to the ingredients label. What's happening is that I'll thicken the water with the Thick-It, but then when I add the Miralax it thins the liquid out to the point where it's not suitable for him to drink. What's going on here chemically?