I was wondering about that. I've taken a number of different cold medications over the years, one active ingredient at a time, to check their effectiveness while sick. Phenylephrine, as widely reported, had zero effect. But Dextromethorphan seemed to work for my kids - give it to them, stopped coughing. Started coughing again 6 hours later, etc. n=1 and it's a 4 year old, but in one of those cases my results clearly matched the studies, and in the other it didn't, at least as reported by this article.