Dextromethorphan
"I'm sick and have a constant barking cough that's mostly unproductive. I read reviews on amazon to find a good OTC cough suppressant. Delsym had rave reviews. I had hubby pick up the orange.

I can say that my coughing has stopped. Delsym absolutely stops the coughing. It's quite wonderful.

What's not wonderful are the three bouts of explosive diarrhea I have had since taking it three hours ago. There's more to come as my stomach is still gurgling. 

This is the really bad stuff. Thank goodness it stops the coughing because if I coughed right now, I'd have diarrhea all over the bed.

The medicine DOES stop the coughing, but it's not worth this kind of diarrhea."