Coughing is a response to various elements affecting the lungs including irritants, inflammation, mucous production and even particulate food or fluid in the airways.
Cough suppressants are supposed to suppress coughs. Expectorants, on the other hand, are supposed to help remove the mucous by making the cough more effective and by increasing mucous production in the lungs and airways in order to make it easier to expel.
Research done on these drugs reveals that many of the suppressants work by numbing the upper airway to the irritating elements mentioned above and do make patients more comfortable and they do cough less. Expectorants on the other hand have not been shown to assist in the removal of mucous from the lungs. The most effective method was found to be physical maneuvers called P, D and C or Percussion, Drainage and Cough. Having the person take deep breaths and simply learn to hack or cough the mucous out. Physical percussion or gentle pounding on the upper thorax area to loosen the mucous also helps.