How are clinical research studies organized?
Clinical studies are performed in four phases. They each look at different questions: • Phase I studies include participants taking a study drug for the first time. Only a small number of people (usually between 20 and 80) are part of Phase I studies. Phase I studies focus on the safety of the study drug and how much of it that may be safe to take in future studies. • Phase II studies take a look at the effect of the study drug on the disease and continue to study its safety. Usually between 100 and 300 subjects participate in a Phase II study. • Phase III studies are done to understand the effectiveness and safety of the study drug or treatment. Phase III studies include large groups of people which can range from 1,000 to 3,000 people or even more. This allows physicians to gain a thorough understanding of the study drug. • Phase IV studies are performed with a drug or treatment that can be prescribed for patients. Phase IV studies are done for many reasons, which include finding out
