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:
- 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 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.
- 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.
