Bisacodyl
"Due to a bacteria which caused traveller diarrhea for like two weeks I had to take very strong antibiotics to get rid of it. Unfortunately, I then couldn't go to the toilet anymore for 4 days. On the 5th day I took one pill at 4pm, woke up at 4am in the morning with really painful stomach cramps, but couldn't go to the toilet. At around 8am the pain was almost unbearable and I felt sick and didn't know if I had to vomit whilst I was sitting on the toilet. Worked eventually but only 16 hours later with a lot of pain in the hours beforehand. It does its job but you have to accept the pain which comes with it."