Robitussin Chesty Cough Medicine helps get rid of the symptoms of a cough or sore throat from the start. It is fast acting and specially designed to reduce congestion, clear nasal blockage, and improve breathing. Robitussin Chesty Cough Medicine contains the active ingredient guaifenesin. This belongs to a group of medicines called cough expectorants that working to break up and loosen the mucus on the chest and reduce coughing. This syrup pr s relief from chesty coughs.