My doctor prescribed me Guaifenex for a sinus infection along with trimethobenx for upset stomach along with advair ( a powder inhaler) never knew why she prescribed all of this medication just for a sinus infection. I stopped taken the advair an experienced shortness of breath, bad headaches, but one things for sure I only eat one meal a day. Oh by the way I can't sleep at night and extremely tired in the morning to start the cycle all over again the next day. It leave a very nasty taste in my mouth i'm constantly brushing my tongue it leave a coating on it. The drainage I can never cough up and my ears has been clogged since I started these meds. I take tylenol pm just to sleep. Something to think about before taking this medication. You get it for a sinus infection but end up with a headache.