Yes you can. Nasonex is actually an inhaled nasal steroid. It helps cut down on the inflammation in your mucous membranes and is absorbed through the nasal passages. Mucinex is a drug which thins out secretions, so if you have sinus and/or chest congestion, it will help thin it out and lessen the pressure or help you cough it up. The "DM" next to Mucinex means it has an added ingredient to help with coughing. Nasonex and Mucinex work in different ways, they are completely different medications. They are safe to take together.