Magnesium hydroxide
"I've never had problems with my bowel movements. However, I just had to have surgery and was taking a narcotic - mostly to sleep at night. 

I had a small bowel movement the third night home, but then felt horribly constipated. 

It was almost worse than the operation. 

It was painful, uncomfortable in my belly and bloating. I took olive oil, ate fruit, did all the things to get my body moving. I walked around for hours. Still, nothing. 

Finally, my mother came over with The Phillips Milk of M and I took the largest amount. Nothing right away. I became frustrated and took another two tsp. about three hours into waiting. 

Exactly six hours after I took the first dose my system finally kicked in - BIG TIME. It was really painful, but RELIEF."