Pharmacists ranked the over-the-counter expectorant Mucinex more highly than they did Robitussin, as of 2014, according to U.S. News & World Report. Mucinex garnered 78 percent of the pharmacists' votes in the survey.
Expectorants typically rely on medications such as guaifenesin to thin mucus and phlegm, to make it easier to cough out of the respiratory system, as WebMD explains. Drinking water can also be helpful to clear phlegm, and expectorants can provoke side effects that include nausea and vomiting. Many over-the-counter cough medicines combine expectorants with cough suppressants to stop the cough reflex. They may also include antihistamines, decongestants and pain relievers to treat related cold symptoms.