Magnesium hydroxide
"This stuff definitely works. I'm 27 weeks pregnant and have been backed up for the better part of the last two weeks. I'm scared to take anything as far as medications because this is my first and I don't want to chance anything,   Like someone else said, take as recommended and drink water!! Don't over do it it may take as long at 6 hours. And DO NOT take of you have somewhere to be. I would describe this as cramp free for sure, but I would say you may be confused if you're peeing or not. You're probably not peeing, and it's definitely working. Will definitely be replacing my regular laxative!! Oh and it's a little chalky, but not terrible if you shoot it."