Magnesium citrate
"This stuff worked incredibly fast, within 20 minutes.  I hadn't had a bowel movement for days, but within 20 minutes, I had a large bowel motion.  Then nothing happened for hours, but during the night I could tell the magnesium citrate was working and in the morning I had to go two or three times.  After the initial movement though you're essentially pooping out dirty water into the bowel.  As other people have said, buy baby wipes and drink lots of water.  And the taste wasn't bad at all! I mixed it with a little bit of cranberry juice and actually found it very sweet/tart and delicious."