Dextromethorphan
"I had a long term chronic cough a few years back & was buying everything on the shelf, nothing worked.  My hubby asked the Pharmacist what he would recommend & he said Delsym the orange stuff, thought it was expensive but bought it.  I immediately stopped coughing.  Well here I am coughing again for a long time & finally broke down & bought some, no more cough with one dose & may take a dose today.  Thanks for this great product."