Cough Medicines

Cough Medicines

A 2004 report in the journal Pediatrics questioned the effectiveness of over-the-counter children's cough medicines. In this Science Update, you'll hear more about the study, and why some medicines may have escaped this sort of rigorous testing.


Why cough medicine isn't always the best medicine. I'm Bob Hirshon and this is Science Update.

According to a recent study by the Penn State College of Medicine, children's cough syrups don't necessarily stop children's coughs. In fact, two of the most common active ingredients worked about as well as a placebo.

We asked lead author Ian Paul how these old standbys could flunk a simple test. He says being an old standby isn't always a good thing.


These drugs are so old–both the medicines that we studied here have been around for about fifty years, that they’ve bypassed all of the regulatory mechanisms that exist today. So I suspect that right now, if today's standards were applied, these drugs don't have enough evidence in the medical literature that they would be approved.

What's more, he says the children's dosages are crudely estimated from adult dosages, and aren't necessarily accurate.

Dr. Paul says there are some proven ways to make a coughing child more comfortable, like giving non-aspirin fever reducers.


And then there's other things that may not help a child with an illness like this, but certainly won't hurt. Things like pushing fluids, giving kids things they like to drink, using salt-water nose drops or nose spray to help thin out nasal mucus, or using a humidifier or vaporizer to kind of moisten the respiratory tract.

These techniques may help relieve symptoms without the risk of side effects. I'm Bob Hirshon for AAAS, the Science Society.

Making Sense of the Research

You might assume that any medicine you find on the counter in the store must have been proven effective. After all, in order to make it onto the shelves, a drug has to clear all sorts of regulatory hurdles set up by the Food and Drug Administration (FDA). These FDA laws require that new medicines–prescription or over-the-counter–must be proven safe and effective.

However, there are a lot of cracks in that system. For one thing, being "safe" doesn't mean there are no side effects. Just about every medicine has side effects. The question is whether the side effects outweigh the possible benefits. (Chemotherapy drugs, for instance, are extremely toxic, but sometimes can stop the spread of cancer.) What's more, most medicines don’t work equally well in all people. Some people may be unresponsive to a medicine, or even allergic. Some kinds of "medicines"–like herbal remedies–are not regulated by the FDA at all.

And then there are drugs like dextromethorphan and diphenhydramine, the two ingredients in cough medicines that Paul's team tested. Dextromethorphan is a cough suppressant, and diphenhydramine is an antihistamine (a useful allergy drug) that is often used in cough syrups as well. These drugs came on the market before most of the FDA's strict regulations went into effect. Therefore, they had never been held to modern standards. In recent years, doctors have become so suspicious of them that the American Academy of Pediatrics stopped endorsing over-the-counter cough medicines for the treatment of children's coughs.

So Paul and his colleagues decided to belatedly test these two popular ingredients. Their study involved both children with coughs and their parents. On the first night, the children weren't given any medicine at all. On the second night, the parents gave their children one of three possible syrups: one with dextromethorphan, one with diphenhydramine, and one plain sugar solution. Neither the parents nor the children knew which syrup they were getting. Yet in each case, the parents reported that the children's symptoms had improved about equally well. The parents themselves even reported sleeping better–whether their children got the real medicine or the placebo.

Dr. Paul says that the two drugs have been tested, way back when, but probably not as extensively or rigorously as consumer laws would demand today. And he also notes that the children’s doses follow a broad rule-of-thumb: half the dose for ages 6 to 11, a quarter of the dose for ages 2 to 5. But Paul points out that there's a big difference between a six-year-old and an eleven-year-old. If children need smaller doses of medicine, shouldn't we be more careful about matching the dose to their actual body size?

Paul's study shows that just because a product is on the shelves doesn't mean it really works. In an age when more and more products are being sold as medicines, consumers need to do their homework and learn what scientists know–and don't know–about what they plan to put in their bodies.

Now try and answer these questions:

      1. Why did Paul decide to look into the effectiveness of children's cough medicines?
      2. Why did the study suggest that the medicines may not work?
      3. What are some possible reasons why an ineffective medicine can make it onto the shelf in a drugstore?
      4. Do you think this is the last word on this issue? What further studies would you propose to follow up on these findings?

For Educators

The Food and Drug Administration's FDA Office of History page has links to many documents describing the history of drug regulation in the United States.

The Center for Drug Evaluation and Research is the wing of the FDA that evaluates and approves new drugs today.

For more on the placebo effect, check out UCLA's Placebo Research website.

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