DRUGS

http://www.bbc.co.uk/schools/gcsebitesize/science/aqa/drugs_use/drugsrev1.shtml

Drugs are substances that change chemical reactions in the body. Medical drugs relieve disease and illness, and are extensively tested before being used. Recreational drugs such as alcohol and tobacco are taken by people because they like the effects they have on their bodies, but they may be addictive. Cannabis and heroin are illegal recreational drugs that are very addictive.

Developing new drugs

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

1. 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.
2. Drugs that pass the first stage are tested on animals. In the UK, new medicines have to undergo these tests, but it is illegal to test cosmetics and tobacco products on animals. A typical test involves giving a known amount of the substance to the animals, then monitoring them carefully for any side-effects. 
3. Drugs that have passed animal tests are used in clinical trials. They are tested on healthy volunteers to check they are safe. Very low doses of the drug are given to begin with. If there are no problems, further clinical trials are done to find the optimum dose for the drug.

Clinical trials are not without risk. Sometimes severe and unexpected side effects occur. Most substances do not pass all of the tests and trials, so drug development is expensive and takes a long time.

Double blind trials

It is important to be certain that a drug really does have positive effects, rather than people feeling better simply because they expect to feel better if they take a medicine. This is called the placebo effect.

Double blind trials aim to minimise the placebo effect. Some patients are given the drug while others are given a placebo. A placebo is designed to appear exactly the same as the drug itself, but it does not actually contain any of the drug.The doctors and patients are not told who have received the drug and who have received the placebo until the trial is over.

Thalidomide

Thalidomide is a medical drug that caused unexpected and serious damage to unborn babies in the 1950s and 1960s.
Thalidomide was developed as a sleeping pill, but it was also thought to be useful for easing morning sickness in pregnant women. Unfortunately, it had not been tested for use in this way.

Birth defects

A boy with stunted growth to the arms and legs due to the effects of thalidomide

By 1960 thalidomide was found to damage the development of unborn babies, especially if it had been taken in the first four to eight weeks of pregnancy. The drug led to the arms or legs of the babies being very short or incompletely formed. More than 10,000 babies were affected around the world.
As a result of this disaster, thalidomide was banned. Drug testing was also made more rigorous than before.