Guaifenesin is effective in the treatment of the thickened bronchial mucosa characteristic of asthma. It works by drawing water into the bronchi. The water both thins mucus and lubricates the airway, facilitating the removal of mucus by coughing. One may notice a sense of dry mouth when taking this medication. Water consumption is important, not only to help with dry mouth, but also to improve the effectiveness of the drug.