Codeine is a narcotic cough suppressant. It affects the signals in the brain that trigger cough reflex. Guaifenesin is an expectorant. It helps loosen congestion in your chest and throat, making it easier to cough out through your mouth. Summary of Use during Lactation. Maternal use of codeine during breastfeeding can cause infant drowsiness, central nervous system depression and even death, with pharmacogenetics possibly playing a role.[1][2] Newborn infants seem to be particularly sensitive to the effects of even small dosages of narcotic analgesics. Dextromethorphan is an over-the-counter medication used to treat cough. Dextromethorphan is available under the following different brand names: Balminil DM, Benylin DM, Bronchophan, Buckleys D, Calylin 1, Delsym, Koffex DM, Novahistex DM, Robitussin Lingering Cold Long-Acting Cough, Robitussin lingering Cold Long-Acting CoughGels, Children's. Codeine is also known as Tylenol 3, Tylenol with codeine, Robitussin A-C, Fiorinal with codeine, Triacin-C, Tuaistra XR, Codate, Codophos syrup, Promethazine with codeine cough syrup and other formulations.