You've probably seen the two-letter "codes" on many over-the-counter cold and flu medications, like Sudafed "PE," or Robitussin "DM." Those letters indicate an ingredient in that medication; however, it may not be the only active ingredient in that formula, so you must read labels carefully.
"DM" in cold and flu medicines stands for Dextromethorphan HBr, which is a cough suppressant. If the cold or flu formula has these letters after its name, you know that it will treat a cough. Other active ingredients may be present as well.
Other Ingredients in DM Preparations
A medication that says "DM" is not just a cough suppressant. For example, Robitussin DM also contains an expectorant, Guaifenesin, which helps your cough to bring up phlegm or mucus from your lungs (sometimes referred to as a "productive" cough.
A multi-symptom cold or flu remedy can contain Dextromethorphan without being labeled "DM." For example, TYLENOL Cold Multi-Symptom Severe contains the decongestant Phenylephrine (the "PE"), Dextromethorphan and a pain reliever (Acetaminophen).
Brands Without Codes
Dimetapp brand recently stopped using the letter codes because they caused confusion. Some brands, such as Tylenol, have chosen not to use codes at all. They simply use names describing the symptoms the medicine will treat, such as Tylenol Cough and Sore Throat.
Take Only What You Need
Doctors recommend that you purchase and take only the medications needed for the symptoms you currently have. If you have a cold without a cough, you do not need a DM preparation (or any cold medicine containing a cough suppressant). You can find another one that better fits your symptoms.