Phases of the clinical trials:  

Clinical trials are a kind of clinical researched designed to evaluate and test new interventions such as psychotherapy or medications.  Clinical trials are often conducted in four phases.  The trials at each phase have a different purpose and help scientists answer different questions.


Phase I Trials

Researchers test an experimental drug or treatment in a small group of people for the first time.  The researchers evaluate the treatment's safety, determine a safe dosage range, and identify side effects.


Phase II Trials

The experimental drug or treatment is given to a larger group of people to see if it is effective and to further evaluate its safety.


Phase III Trials

The experimental drug or treatment is given to large groups of people.  Researchers confirm its effectiveness, monitor side effects, compare it to commonly used treatments, and collect information that will allow the experimental drug or treatment to be used safely.


Phase IV Trials

Post-marketing studies, which are conducted after treatment is approved for use by the FDA, provide additional information including the treatment or drug's risks, benefits, and best use.