- Diphenhydramine – reduces allergy symptoms and can suppress coughing; it may also cause drowsiness.
- Ammonium chloride / Guaifenesin / Ambroxol – help loosen and thin mucus so it can be coughed out more easily.
- Menthol – gives a cooling, soothing effect in the throat.
- Terbutaline (in some cough syrups) – helps open the airways and makes breathing easier.

