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Keeping healthy

Drug testing


Antibiotics are drugs that kill bacteria, but not viruses. Certain antibiotics can be used to treat fungal infections, such as thrush.


Drugs are substances that cause changes to the body. Some can help the body, others can harm it. Certain drugs can be extracted from natural sources and their existence has been known of for a long time. For example, willow bark was used by the ancient Greeks to help cure fevers and pains. It was later discovered that the active ingredient was salicylic acid. This was modified by chemists into the substance we call aspirin, which is less irritating to the stomach than salicylic acid.

salicylic acid and aspirin molecules

Drug testing

New medical drugs have to be tested to ensure they work and are safe before they can be prescribed. There are three main stages:

  • The drugs are tested using computer models and human cells grown in the laboratory. Many substances fail this test because they damage cells or do not seem to work.
  • Drugs that pass the first stage are tested on animals. In the UK, new medicines have to be. But it is illegal to test cosmetics and tobacco products on them. A typical test involves giving a known amount of the substance to the animals, then monitoring them carefully for any side-effects.
  • Drugs that have passed animal tests are used in clinical trials. They are tested on healthy volunteers to check they are safe. The substances are then tested on people with the illness to ensure they are safe and work.


You may wish to view this BBC News item from 2006 about a drugs trial that left six volunteers very ill.

Most substances do not pass all the tests and trials, so drug development is expensive and takes a long time.

Medical drug trials are not without risk. Sometimes severe and unexpected side-effects occur.

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