Miralax for colonoscopy prep-stuffy nose and vomiting

I took about 2/3 of the 64 ounce Gatorade mixed with Miralax that I was supposed to take and was not having a problem getting it down. All of a sudden I got a very stuffy nose (unusual for me) and then threw up with almost no warning. I proceeded to bring up what had to be all of the solution I had downed. Has anyone heard of this? Could it be an allergic reaction? I have several allergies, mostly to antibiotics.