Clinical Trials

What are Clinical trials?

Before any new medical treatment can be put into wide use it has to be tested for safety and effectiveness. A clinical trial is a research study which does this by testing a new treatment on human beings.


Who organises them?

Doctors will carry out the clinical trial, but in many cases they are organised and paid for by pharmaceutical (drug) companies. The researchers should always tell you if the trial is being funded by a pharmaceutical company.  

Are they safe?

All medical treatment involves some level of risk, even something as everyday as taking paracetamol or aspirin. If you take part in a clinical trial you will be having some kind of medical treatment which you would not otherwise have. This treatment may make you feel better but it could possibly also cause side effects. Most of the time these side effects are likely to be very mild, but in rare cases they could be serious.
If you are asked to take part in a clinical trial you should make sure you are told what phase of trial it is (see below). This will give you a clearer idea of what is involved and the level of risk you are taking in terms of the possibility of side effects. The researcher must tell you everything they can about possible side effects and then the decision whether to take part will be yours. See Risks and benefits for more information.


If you are part of a clinical trial to test a new medicine, you may be given a card (the size of a credit card) contains details of the study and the medication which you are taking. This card should be carried with you at all times.

During a clinical trial you should also have a contact name and number for any concerns during the study. This includes details of how to report any ill health which you experience whether or not you think this might be related to the study treatment.

It is possible that new information about the study treatment or medication may become available to the researchers during the study. If this happens they should contact you and discuss whether you want to continue in the study. If you do decide to continue you will need to sign a new consent form. If you decide not to continue the research doctor will make arrangements for your care to continue.


Types of clinical trials


Phase 1 trials

Phase 1 trials are studies of treatments which are being tested on humans for the first time. The treatment will already have had many safety tests in the laboratory. Scientists will believe that the treatment is safe to use in humans, but they need to gather more evidence to prove this.

Usually a small group of healthy volunteers will be offered the treatment at this stage because of the high risks involved. Many phase 1 trials are carried out in special clinical trial centres where research subjects are carefully monitored and sometimes paid for their involvement.

Occasionally this type of study is carried out among patients who have a life threatening illness where no other treatment is currently available. Patients may decide to take part because the treatment offers them the best possibility of improved health.

Researchers will be looking for

  • Side effects of the treatment
  • Whether the treatment works (not possible if healthy volunteers are being studied)
  • What is a safe dose of the treatment


Phase 2 trials

If a new treatment can be shown to be effective and safe after a phase 1 trial, it will continue to phase 2.

Taking part in a phase 2 study has fewer risks than phase 1. By this point researchers will know a lot more about the effects of the treatment on humans and will be ready to test it on a larger group of patients or healthy volunteers.

During a phase 2 study the researcher will be looking at:

  • Minor side effects of the treatment.
  • How well the treatment works.
  • And possibly, alternative ways of giving the treatment ( eg injection versus tablets)


Phase 3 trials

If the results of a phase 2 trial are good then a phase 3 trial will often follow. Much more is now known about the new treatment and so the risk of unexpected problems is smaller. For this reason it is seen as safe to carry out a trial involving a larger number of patients, often 100's or even 1000's from many different hospitals.

The main purpose of phase 3 studies is to compare the new treatment with the most commonly used existing treatment.

Researchers may want to find out:

  • Whether the treatment is more effective than the existing treatment.
  • Whether the treatment has more or fewer side effects than the existing treatment.
  • The long term benefit of the treatment to the patient.
  • Whether the patient's quality of life is improved by the treatment.

Phase 3 studies are always randomised. This means splitting patients into two or more groups, each of which will receive a different treatment. The purpose is to compare the new treatment with other existing treatments for the same condition.


Phase 4 trial

Once the three phases of clinical trial are complete, the new medication will go on sale. At this point the pharmaceutical company might fund a phase 4 trial. The main purpose of this type of trial is to promote their drug and bring it to the attention of more doctors. There are few risks involved in a phase 4 trial because much is already known about the treatment. This kind of trial is of less scientific importance than earlier phases.


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