Bisacodyl
"I've taken dulcolax before and didn't have a bad experience so I wasn't prepared for what was to come. I was slightly constipated and had to call into work yesterday due to really painful cramps so last night I took ONE dulcolax around 10pm, had a midnight snack (easy mac) and then fell asleep. I don't even remember getting to the toilet but all of a sudden I was on the toilet and it was like a tap  turned on full and cringing in pain  from my stomach, I was so weak, dizzy, sweaty, once the diarrhea would stop I'd tumble off the toilet onto the floor and lay in the fetal position crying. Thank God for my boyfriend he got me a water and a plastic bin so I could poo and vomit at the same time. It was miserable. It's 1130a now and I'm still having cramps"