How Are Clinical Trials Organized?
Drugs and procedures don't advance to clinical trials unless they show some significant promise of improving or preventing a condition and researchers think their rewards outweigh their risks. Clinical trials involve human subjects, and they are carefully designed to assure effectiveness and safety.
Phase I Trials
In the first phase of human testing, researchers test an experimental drug or treatment in a small number of volunteers (fewer than 100). They study safety, risks, and side effects. Phase I trials generally last only a few months.
Fact
Researchers often submit data to the U.S. Food and Drug Administration (FDA) for review and approval during Phase III trials. Most drugs undergo two successful Phase III trials before the FDA approves them, according to health and safety authorities at the National Institutes of Health.
Phase II Trials
If an experimental drug or treatment fulfills criteria in Phase I, it moves to Phase II trials, which typically enroll a few hundred volunteers. The treatment is tested for safety and efficacy among a larger group of people (typically between 100 and 300) over longer periods of time.
Phase III Trials
Drugs and treatments that pass muster in the earlier trials are tested in large groups of hundreds or thousands of patients, depending on what is being studied. Phase III trials are designed to definitively evaluate the effectiveness of a drug or treatment, and to compare it with the best current treatments and practices.
Phase IV Trials
Phase IV trials, also known as post-marketing surveillance trials, monitor the safety, risks, benefits, and competitive advantages of an FDA-approved drug that is already on the market.
