You may have been drinking yucky cough medicines all these years for nothing.  In 2010 a study showed that there was no evidence to suggest the effectiveness of over the counter cough medicines and cough suppressants, such as dextromethorphan, or expectorants like guaifenesin... Sometimes your cough medicine isn’t working because it isn’t the right one for the type of cough you have.  In Chinese medicine we identify several different types of cough, hot, cold, excess, deficient, wind dry, damp phlegm, etc...