Because of the impaired cough reflex the combined use of acetylcysteine together with antitussives may lead to a dangerous congestion of the mucous secretion, which means that the indication for such a combined treatment must be worked out very carefully. Tetracycline hydrochloride should be administered separately and at least 2 hours apart (not valid for Doxycycline).
Until now, reports on the inactivating effect of acetylcysteine or other mucolytic agents for antibiotics were only found in connection with in-vitro tests where the respective substances were mixed directly. Nevertheless, for security reasons the oral administration of antibiotics should take place separately and after a delay of at least 2 hours. In vitro-interactions are described previously all for semisynthetic penicillin, tetracycline, cephalosporins as well as aminoglycosides. For antibiotics as amoxycline, doxycycline, erythromycin, or thiamphenicol, as well as cefuroxime, no interactions were reported here.
There have been reports on an increase of the vasodilating and platelet aggregation inhibiting effect of trinitroglycerin (nitroglycerin) under concomitant application with acetylcysteine. A judgment with regard to the clinical relevance is, however, not yet possible for the time being.