A clinical trial, also called a research study, is a process scientists use to test the value and safety of various interventions in people. Clinical trials are meant to find new and improved methods of evaluating or treating a condition or it can test a new way to prevent diseases.
Clinical trials are conducted in phases and may span long periods of time.
Phase I clinical trials involve giving a new treatment to a small number of participants. The researchers determine the best way to give the new treatment, how much of it can be given safely, and help identify possible side effects. Participants are usually people who would not be helped by other known treatments or alternatively, a phase I trial is performed in healthy volunteers to determine the safety of a particular treatment.
Phase II clinical trials focus on learning whether the new treatment has an effect on a specific condition. Additional information regarding the side effects and safety of the treatment is also obtained. A small number of people are included because of the risks and unknowns involved.
Phase III clinical trials compare the new treatment with the standard treatment. In this phase, researchers determine which study group has fewer side effects and is undergoing the most improvement.
Phase IV clinical trials, also called post-marketing studies, are conducted after a treatment has been approved. The purpose of these trials is to learn more details about the treatment and to address questions that may have come up during other phases of trials.