Mucinex (aka guaifenesin) is an over-the-counter medication that is often used to treat cough and other symptoms of upper respiratory illnesses (URI). However, this medication unfortunately is also often used to treat other symptoms inappropriately. It is believed to work by increasing the volume of secretions thereby reducing the viscosity of thick secretions that may be present in the trachea and bronchi with URI. (To use an analogy, it's like adding water to syrup to thin it out.) …