NAC is a natural product derived from cysteine. Inactivations of some antibiotics have been observed in vitro when mixed with N-acetylcysteine such as semi-synthetic penicillins, tetracyclines, cephalosporins and aminoglycosides. When on these medications it is recommended taking 2 hours apart from PharmaNAC dosing. For antibiotics such as amoxicillin, doxycycline, erythromycin, thiamphenicole and cefuroxime no incompatibilities were found. We do however recommend consulting your doctor first when taking NAC with other medications.