I have chronic. if I may: after months, over an year, I took 1200mg of NAC a day for ten days and then 600mg everyday — actually, every night before sleep. I’ve never felt better (after two weeks) in a whole fkn while. no more coughing (that used to be the first thing I did as soon as I woke up for only getting outta bed), no more pain, breathing simply flows like it used to (before 28 years smoking two packs a day).