I've had a cold the last week and a half and the last two days I took some phenylephrine thinking it would be good for my sinuses and subsequently my voice. BIG FUCKING MISTAKE. This shit flat destroys your voice in a way nothing else I have ever experienced can. Avoid this crap at all costs. I really really sounded like shit after taking this crap. I'm glad I found out now and not by ruining a gig or something in the future. I mean this stuff is so bad that if you can sound even remotely decent after taking it you can sound good because of anything. I feel a lot better today not taking this garbage. You just can't beat chronic use of Afrin though, that stuff actually improves things in ever way.
I know I'm supposed to post this kind of info in the other thread, but people need to read this:
PHENYLEPHRINE found in cold and sinus products or even on it's own is a bad bad bad idea.