I had a sinus infection with a slight ear infection a few months ago, in April. I was prescribed Guaifen PSE and Biaxin, an antibiotic. Within the past couple of days I have been feeling very ill and attempted to take the Guaifen - only to realize that I had forgotten about the horrible side effects of last time!
This medicine was very rough on my body. When taking it, I feel very stange, and can not sleep more than 30 minutes at a time no matter how long I have been awake. The first day of taking the medicine, I had to urinate every 15 minutes for the first 8 hours or so, no matter how much or how little liquid I ingested. My mouth is very dry, and after a few days of taking this medicine, my skin became dry and cracked, mostly around my hands and face. I developed a bumpy, red rash on my face after about a week, though I am not sure whether this was from the Biaxin or the Guaifen. It did cause extremely severe coughing fits after the first few days of taking it, which often were bad enough to lead to vomiting.
That said, it does clear up nasal congestion - if you want to be blowing your nose every five seconds. It will drain out every bit of fluid in your body. You have to be feeling pretty bad to take this stuff.