Key takeaways
Mucinex DM (guaifenesin/dextromethorphan) and Deconex DMX (dextromethorphan/guaifenesin/phenylephrine) are both over-the-counter medications used to relieve cough and congestion, but they have some differences. Mucinex DM combines an expectorant (guaifenesin) to thin mucus and a cough suppressant (dextromethorphan) to reduce your urge to cough. It’s available in many different forms, each with different dosages, directions, and age limits. Mucinex DM is taken every 4 to 12 hours, depending on the formulation. Deconex DMX has the same ingredients as Mucinex DM, as well as a decongestant (phenylephrine) to help relieve nasal congestion. Deconex DMX needs to be taken more frequently, every 4 to 6 hours. Neither medication should be taken in children less than 4 years old. Mucinex DM is generally better tolerated with fewer common side effects, whereas Deconex DMX can cause dizziness, sleepiness, and headache.
