About clinical trials

Clinical trials are used to gain further medical knowledge. Clinical trials can be used to assess the effectiveness and side effects of new medicines, improve the use of existing medicines or find new uses for existing medicines.

Clinical trials are divided into different phases. There are 4 main phases, as described by the Food and Drug Administration (FDA);

  • Phase 1 – Studies that involve healthy individuals. These studies are mainly set up to determine the safety of the investigational drug; what are the most common side effects? How does the body metabolize the product?
  • Phase 2 – Studies that involve small groups of patients with a particular problem. These studies determine the safety and effectiveness of the drug, and look at the short-term effects of using the drug.
  • Phase 3 – Studies that enrol large numbers of patients from different populations with a particular problem. These studies gather more information on the safety and efficacy of the drug, different dosages of the drug and different drug combination
  • Phase 4 – These studies are usually performed after the drug has been approved for use. These studies continue to gather information on the safety and effectiveness of the drug, but also determine its optimal use.

Clinical trials that involve children generally start at Phase 2 or 3

Things to remember

Clinical trials are not for everyone
− Each study has certain criteria that a person needs to meet in order to participate

Even though it is approved for adults, the study drug is still under investigation in children
− There may be unknown side effects

The participation in a clinical study is voluntary
− Patients can leave the study at any time



UK information on clinical trials


UK Clinical Research Network UKCRN