How can a cough syrup be both a cough suppressant and an expectorant? Aren’t these opposites? I can only WAG that such medicines help loosen congestion in a gentle manner to make your minimized cough more productive. Is this correct? - Jinx
You are probably talking about Robitussin DM. This is a cough suppressant as well as an expectorant. It has two active ingredients, dextromethorphan (which is a derivative of morphine, cousin of codeine, and works pretty well) as well as guaifenisen (which is touted as an expectorant - that means it helps thin out the phlegm in your lungs and “expel” it outwards). Guaifenisen is kind of controversial because no one seems to be able to prove that it does anything.
Actually,a suppressant is to stop uncontrolled coughing while an expectorant is to allow you to cough up mucus when you intend to.