Dextromethorphan
"DIARRHEA. Remember that word, because if you take this stuff, you will be suddenly awaken during the middle of the night and forced to wreak havoc on your toilet bowl. I just blew up my toilet 45 min ago and am getting ready to pay it another visit as I write this. If you are reading this review, take my advice: use something else.  My cough was bad, but I would have gladly kept it if I knew my butt was going to turn into Niagara Falls."