Bisacodyl
"This is the worst medicine I have ever taken. I had to do prep for a colonoscopy.  It came time to take this medicine, I was in so much pain, that I almost went to the hospital prior to my test. I thought something went terribly wrong. Hours upon hours of violent diarrhea and cramps like I have never felt before in my life. The sweats were terrible. I actually pooped my pants the following morning as this med had taken over my entire digestive system. I had no control of my bowels. Not normal for a 37 yo.. I had to drive to the test with a towel between my bottom cheeks for fear of pooping myself again. DO NOT TAKE THIS unless you enjoy unbearable pain!!!!"