Clinical trials and their different stages

Clinical trials test if a new medicine is safe and how effective it is. 

The phases of clinical trials

All clinical trials of new medicines go through a series 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 1 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 do not experience any side effects, or if they only experience minor side effects.

Phase 2 trials:

The new medicine is tested on a larger group of people who are ill. This phase determines the most effective dose. This is to get a better idea of its effects in the short term.

Phase 3 trials:

Carried out on medicines that have passed phases 1 and 2.

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 4 trials:

The safety, side effects and effectiveness of the medicine continue to be studied while it's 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 is 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 will be given the treatment being assessed, or

control group - where you will be given an existing standard treatment, or a placebo if no proven standard treatment exists

While the treatments are different in the 2 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.

Read more about taking part in research at PID UK here.

Posted 1st December 2020