I took Mucinex DM last night around 1 am and felt strange soon after, but by 6 am I had diarrhea, dizziness, rapid heartbeat, difficulty breathing, and chills. It did help my cough, but this product is certainly not worth the side effects. From all the similar stories I've read on here, I think this product shouldn't even be on the market. I'd much rather suffer through some congestion than to feel that terrible again. I mean, I seriously thought I was going to die. Never using Mucinex again.