Bisacodyl
"Worst ever experience!! Do not take this unless you like pain, nausea and a severe burning sensation in your stomach and intestines! Took the pills at 9 pm with water as directed. Woke up at 2 am sick as can be. It's 4:30am, I'm wide awake and sick. If this is no better by 8 am, I am calling my doctor to see if there is anything I can take for some relief!!"