Matching Side Effects

Matching Side Effects

Drugs that share side effects also may have similar benefits.


Teaching old drugs new tricks. I'm Bob Hirshon and this is Science Update.

Many drugs turn out to have multiple uses: for example, Viagra was originally a heart medication. Now, German and Danish scientists have developed a way to look for these alternate applications, by analyzing the drugs' side effects.

Peer Bork of the European Molecular Biology Laboratory and his colleagues found that drugs that share many side effects often share desirable attributes as well.


Many drugs that usually don't have anything to do with each other, they are likely to share targets: common proteins where they bind to.

That suggests that the drugs may be able to do each other's work—and if one is cheaper, better, or less toxic than the other, all the better. Bork adds that such drugs will already have been tested and cleared for use in humans. I'm Bob Hirshon for AAAS, the Science Society.

Making Sense of the Research

Listening to the long list of possible side effects at the end of any drug commercial can cause dizziness, confusion, and anxiety. Although many of the side effects may be rare, they illustrate how many different changes a single chemical can trigger in the body.

Some side effects, like headache and nausea, are extremely common; you may be hard pressed to find a drug that doesn't list one of these as a possible side effect. However, Bork and his colleagues weren't just comparing drugs that shared individual side effects. Rather, they looked for drugs that shared similar constellations of side effects: for example, a pair of drugs that shared 19 of 25 side effects on their respective lists.

Aside from the side effect information, the researchers also factored in the drugs' known molecular targets. Many drugs are formulated to act on a particular molecule in the body. However, the same drug may act on other body chemicals that its developers weren't aware of. The researchers' hypothesis was that drugs that share chemical targets will produce similar side effects, and therefore, the reverse is also true: drugs that produce similar side effects may have shared chemical targets.

Bork's team looked at 746 drugs that are currently on the market, and identified 261 that, according to their analysis, may have additional therapeutic benefits. They tested this principle on 20 of those drugs, and found that 13 did in fact bind to the molecular targets the researchers predicted. That doesn't mean that they would necessarily be useful in treating new conditions, but it's certainly a promising lead.

As the story reports, finding new uses for existing drugs could save a lot of money and time. Drug development is extraordinarily expensive, and ten or more years can pass between a drug's invention and its introduction into the mass market. That's because new drugs have to go through a rigorous approval process, starting with laboratory and animal studies, moving on to basic safety testing in people, and finally to clinical experiments that determine whether the drug actually works. Many of these steps can be skipped if you're simply testing a new use for a drug that's already approved. As health care costs continue to rise, this technique could offer a medical equivalent for the environmental slogan “Reduce. Re-use. Recycle.”

Now try and answer these questions:

  1. State the researchers' basic hypothesis.
  2. How did they compare side effects of the drugs?
  3. What is the relationship between side effects and therapeutic (medical) benefits?
  4. If, for example, this technique showed that an antidepressant also acted on the same molecular target as a popular heart medication, what else would need to be proven before the antidepressant would be used to treat heart conditions?

You may want to check out the August 1, 2008 Science Update Podcast to hear further information about this Science Update and the other programs for this week. This podcast's topics include: why some wounds form scars, buying soldiers time on the battlefield, and the surprising upside of drug side effects.

Going Further

For Educators

National Geographic News features the following articles on the potential medical benefits of toxic snake and snail venoms:

In the Science NetLinks Science Update lesson Hearts and Worms, students learn how a worm that has no heart is helping scientists figure out why potentially beneficial drugs may have deadly heart reactions in humans.

The page Neurotransmitters as “Lock and Key”, from Biology in Motion, features a one-page cartoon and description of neurotransmitters and how they cause changes in cells. Many drugs work by either mimicking or blocking neurotransmitters.

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