Testing a new medicine
All clinical trials of new medicines go through a 3series of phases to test whether they are safe and whether they work.
The medicines will usually be tested against another treatment called a control. This will either be a dummy treatment (a placebo) or a standard treatment already in use.
Phase one trials:
- A small number of people, who may be healthy volunteers, are given the medicine.
- The drug is being trialled in human volunteers for the first time.
- Researchers test for side effects and calculate what the right dose might be to use in treatment.
- Researchers start with small doses and only increase the dose if the volunteers don’t experience any side effects, or if they only experience minor side effects.
Phase two trials:
- The new medicine is tested on a larger group of people who are ill. This is to get a better idea of its effects in the short term.
Phase three trials:
- Carried out on medicines that have passed phases one and two.
- The medicine is tested in larger groups of people who are ill, and compared against an existing treatment or a placebo to see if it’s better in practice and if it has important side effects.
- Trials often last a year or more and involve several thousand patients.
Phase four trials:
- The safety, side effects and effectiveness of the medicine continue to be studied while it is being used in practice.
- Not required for every medicine.
- Only carried out on medicines that have passed all the previous stages and have been given marketing licences – a licence means the medicine can be made available on prescription.
Control groups, randomisation and blinding
If you take part in a clinical trial, you will usually be randomly assigned to either the:
- treatment group– where you’ll be given the treatment being assessed, or
- control group– where you’ll be given an existing standard treatment, or a placebo if no proven standard treatment exists
While the treatments are different in the two groups, researchers try to keep as many of the other conditions the same as possible.
For example, both groups should have people of a similar age, with a similar proportion of men and women, who are in similar overall health.
In most trials, a computer will be used to randomly decide which group each patient will be allocated to.
Many trials are set up so nobody knows who’s been allocated to receive which treatment. This is known as blinding, and it helps reduce the effects of bias when comparing the outcomes of the treatments.