There are two main types of over-the-counter cough medicine.
The first type are antitussives. An antitussive is a cough suppressant. Dextromethorphan is one of the more common ingredients in antitussives. It works by partially blocking the cough reflex. It lessens your body’s tendency to allow a cough to be triggered involuntarily.
Some common antitussive over-the-counter cough medicines include Triaminic Cold and Cough, and Vicks 44 Cough and Cold.
The other type of over-the-counter cough medicine is an expectorant. Expectorants work by thinning the mucus that can clog your airway and cause you to cough to clear it.
The main ingredient for over-the-counter expectorants is guaifenesin. Some common expectorant over-the-counter cough medicines include Mucinex and Robitussin Chest Congestion.
(There are also some types of cough medicines with significant amounts of narcotics like codeine, but these stronger cough medicines are only available by prescription.)
With any medication, including fairly tame over-the-counter medications, you always want to be aware of the risk of it interacting adversely with some other medication-over-the-counter or prescription-that you may be taking.
In the case of over-the-counter cough medicine, the primary risk is consuming too much of an ingredient because you’re not aware it’s in multiple medications you’re taking. This happens most often because some products are designed to treat multiple symptoms of, say, a cold. So you need to read your labels and check the ingredients.
For instance, you may be taking something you think of as a cough medicine, when in fact if you look closely you’ll see that it treats other symptoms as well. Then if you’re also taking something else for those other symptoms, you could be inadvertently doubling up. You might be taking, say, an antihistamine, a decongestant, and/or a pain reliever, and if one or more of these is also contained in your cough medicine, then you may exceed the recommended dose.
Or, your cough medicine may indeed be solely a cough medicine, but you may be also taking a general cold remedy which itself contains cough medicine, thus exceeding the recommended dosage in that way.
Beyond that, there is a small risk of an over-the-counter cough medicine interacting adversely with certain prescription drugs. If you are on any prescription medications, always ask your doctor before taking cough medicine, or any other medication.
Specifically, some patients taking a monoamine oxidase inhibitor (MAOI)-a prescription drug used to treat depression among other conditions-have had problematic interactions with over-the-counter cough medicines.
“Cough Medicine: Understanding Your OTC Options.” Family Doctor.
“Cough Medicines and Cough Syrup.” WebMD.