Magnesium citrate
"I had very hard impacted stools that I tried to expel for several hours. My husband bought magnesium citrate and I drank the entire 10 oz bottle. Nothing happened - so I got into a warm bath and I finally was able to get rid of it one inch at a time. (sorry to be so disgusting). Well, 6 hours later, the diarrhea started and went on every 2-3 minutes until I went to bed. I got up this morning and felt better, but again, I have diarrhea and it explodes from me. 
So, the only thing this drug did for me was to give me diarrhea so I will never use it again. Hopefully, if I stay away from cheesey food, I won't need anything like this."