Suppressants do their job by blocking your cough reflex. Dextromethorphan is the most common ingredient for this. You’ll see it listed as DM on the bottle or package.
This type of medication isn’t used to treat a cough with mucus. And it can’t relieve pain like the medicine codeine -- you'll need a doctor’s prescription for cough meds with that in it.
What Do Expectorants Do?
A cough with phlegm can be a good thing -- it clears all the gunk from your airways. But talk to your doctor if it keeps you from sleeping.
Some doctors say drinking water is the best way to get rid of mucus, but you can also use medications like guaifenesin. This drug thins the drainage so it’s easier to move out. The most frequent side effect of this med is nausea and vomiting.
Do Topical Cough Medicines Work?
Camphor and menthol are natural treatments. They usually come in an ointment you rub on your throat and chest. Their strong-smelling vapors may ease your cough and open up your stuffy head.
You can also get them in liquid form to use with a vaporizer, a gadget that makes steam you can breathe in. You’ll find menthol in lozenges and compressed tablets.
What’s a Combination Medicine?
Many over-the-counter treatments mix a suppressant and expectorant with medicines for other symptoms. That could include an antihistamine, a decongestant, and a pain reliever.
The mash-up can be a good thing if you have a range of cold symptoms, like body aches, coughs, and congestion. The downside is that you may get medicine you don’t need.
Is Cough Medicine Safe?
The doctor may tell you not to treat a cough from a cold unless it keeps you up at night or gets in the way of your daily life. Coughing up mucus helps keep your lungs clear. This is especially true if you smoke or have asthma or emphysema.
Dextromethorphan can affect drugs that treat depression. Also, some combination cold and cough medicines contain decongestants, which can raise your blood pressure. So skip them if your BP is high or if you have heart disease.
Bottom line? If you're on any medication, get your doctor’s OK before you try an over-the-counter cough treatment.
SOURCES: National Institute of Allergy and Infectious Diseases: "Common Cold: Treatment." Mayo Clinic: "Common Cold." MedicineNet: "Cough." American Academy of Family Physicians: "Cough Medicine: Understanding Your Options." UptoDate: "The common cold in adults: Treatment and prevention."
Jennifer Robinson, MD on January 22, 2015