Webmucinex d and mucinex dm both contain the expectorant guaifenesin (which is contained as a single ingredient in mucinex). Guaifenesin is an expectorant that helps. Webthe main difference between mucinex, mucinex d, and mucinex dm is the active ingredients in each brand name. Mucinex contains guaifenesin only and is used. Mucinex dm what's the difference? Webwhat is the difference between mucinex d and dm? Mucinex d and mucinex dm both contain guaifenesin as an active ingredient. So, they’re both expectorants, or. It has two active ingredients:
