Guaifenesin
"Recently I had a horrible head cold, it wasn't serious enough to see a doctor so I started taking Mucinex D. The second day I took the pill I noticed I was on the drowsy side and my urine was foul smelling. I took it for three days, about two hours into taking the third pill I started to get leg cramps and horrible abdominal pains that lasted for almost another 24 hours. The pain was awful and made me very nervous. My cold symptoms had subsided, so yes it does work but the side effects were awful."