I got so sick and could not cough up anything so I started the Mucinex. I took it for a month straight and it seemed to work then all of a sudden . . . . bam, could not breath. One Dr. told me to take it to feel better and another Dr. told me only take it 10 days on 10 days off. It could start doing the opposite. That is exactly what it did, I now have another serious lung infection. Trying to figure out what to do is exhausting emotionally and physically. Here is my take, the Pulmonologist was correct . . . . don't take it for long periods of time. It will stop helping and take you the other direction. You could start picking up bacteria again. I did. I feel as if I am wondering blind thru this maze. I figure it out as I go and do the best that I can.