DM (or DXM) cough medicines contain a substance called dextromethorphan. Dextromethorphan (DM) is an antitussive that treats the symptoms of a cough by decreasing chemical activity in the area of the brain that causes coughing. Dextromethorphan does not treat cough caused by asthma or smoking-related illnesses like emphysema. Roughly 140 cough medicines containing DM are available. These medications are available over the counter in a variety of forms.
Solutions and Suspensions
Dextromethorphan cough medicines are available in liquid forms, including a solution and an extended-release (long-acting) oral suspension. According to the Mayo Clinic, the extended-release oral suspension should be taken in doses of 60 mg every 12 hours in adults and children age 12 and above. The suspension should be shaken well before use to ensure it is mixed properly. Those taking the solution are advised to closely follow the dosing instructions on the label and to use the measuring cup or spoon that comes with the medicine instead of a household spoon. Special pediatric liquid formulations are available for children over the age of 4. Label instructions regarding dosing for children should be followed closely. Use is not recommended for children under the age of 4.
Other Oral DM Cough Medicines
Dextromethorphan cough medicines are available in other oral forms, including chewable tablets, dissolving strips and lozenges. A liquid-filled capsule is also available. Strips should be dissolved on the tongue and then swallowed; chewable tablets may be chewed and swallowed or allowed to melt on the tongue before swallowing. Liquid capsules should be swallowed, not chewed, and taken with water according to the dosing specified on the label. The Mayo Clinic advises adults and children age 12 and older to take 5 to 15 mg of the DM lozenges every two to four hours.
Combination DM Cough Medicines
Dextromethorphan is sometimes combined with other medications to treat conditions like allergies, infections, cold and flu that cause multiple symptoms. These medicines are commonly found over the counter in syrup or liquid capsule form. Dextromethorphan medications may contain antihistamines like chlorpheniramine that help relieve or prevent allergy symptoms such as itchy, watery eyes, sneezing and runny nose. They may also contain decongestants like pseudoephedrine hydrochloride that help relieve sinus congestion and headache. Dextromethorphan and the expectorant guaifenesin (a medication that helps bring up mucus from the chest and lungs) are often combined to treat cough and chest congestion. Pain relievers and fever reducers like acetaminophen or aspirin are also commonly combined with dextromethorphan to ease aches and pains associated with cough and cold.
