Bisacodyl
"I've been on painkillers for a week and a half including codeine and tramadol, so I've been really backed up which led to more pain. I've been suffering with a severe kidney infection and a burst ovarian cyst. I took two tablets at 9pm woke up at 2:30 with cramping quite severe but to be honest nothing worse that the pain I've been in with my problems anyways. Feels great to have a  BM yeah it's pure liquid but that's what a laxative does. I would recommend if it's severe constipation you have especially the type codiene gives you!"