Citation? Dextromethorphan works very well for me. (Also DXM is a recreational drug which is why it's always sold OTC with either Tylenol in it or as an extended-release formula)

In the vast majority of cases for my family, Dextromethorphan is a miracle drug. We're in the middle of cold and allergy season here, and my kids (and I) stop coughing within 5-10 minutes of taking an appropriate dose.

Once every 3-4 years I'll get a cough so bad that DXM won't fix, and when that happens my doc gives me a prescription for a codeine based cough syrup that fixes it (and renders me useless as a human being).

Mucinex (Guaifenesin) fixed all my illness cough problems. It makes your mucus thinner and produces more of it to make your coughs "more productive" which means you finally get that junk out of your throat. Eliminates tickly throat coughs and also is useful in pretty much all situations that involve coughing. It's a genuine magic bullet for me, where no cough suppressant has ever worked, through my entire 30ish year existence.