Bisacodyl
"I took 4 in preparation for a colonoscopy tomorrow.  They told me take 4 at 3 pm and then at 5 mix a 14 dose container of miralax with 64 oz of water and drink 8 oz every half hour until it's gone which would take 4 hours. After drinking 1-1/2 quarts I started feeling sick and threw up probably every bit of liquid I drank.  Here it is 7 hours after I took 4 dulcolax and i haven't gone yet.  It's 10 pm.  My colonoscopy is at noon tomorrow.  If I start going I'll be up all night pooping.  Ridiculous.  One thing I want to say after reading others posts.  If you're really going bad use baby wipes to clean yourself after each BM and put vasoline on your butt hole and it won't burn."