CF doctors are probably not going to recommend that someone with CF take something that would keep them from coughing, because that would not be conducive to getting up the mucous. I used to use cough medication and have taken a sip of alcohol to stop coughing, but now I mostly rely on Benadryl. Usually my coughing is from post nasal drip though, and Benadryl really helps dry me out. I doubt it would be recommended for lungs either though.