Benzonatate
"I took one of these tessalon perles for an upper respiratory infection and I thought I was going to die!  I started salivating like I was going to throw up but didn't and at the same time I felt like I was choking to death from deep down in my esophagus or chest area.  I don't know if my hiatal hernia has anything to do with this but I cannot ever take this medication again. I should have went to the ER but I didn't.  It lasted about 3 hours and finally went away on it's own."