bronchitis
"When I was using it in cough syrup without measuring it, I sometimes got a headache.  However, taking the recommended maximum dose of 6 tablets per day (that is, every 4 hours), I have had no side effects except for a bit of mental fuzziness.  It really helps me to expectorate thick mucus. A great side benefit is not having to endure that horrible taste that guaifenesin has!  Very inexpensive (less than 15 cents per day) and very helpful for non-productive cough!"