Bisacodyl
"Last night I was feeling very constipated before I went to bed. So much so that I couldn't get to sleep. So I went to a store near my house and purchased this enema. I gave it to myself as soon as I got home. I then sat on the toilet for the next 45 minutes. I thought after a half an hour that it might never end. Afterwards I was able to lay down and fall right to sleep."