How Do Clinical Trials Work?

Clinical Trial Regulation and Phases

How Clinical Trials Are Regulated
In the United States, all clinical trials are approved, regulated, and monitored by an Institutional Review Board (IRB), which is under the control of the US Food and Drug Administration (FDA). An IRB is made up of independent doctors and other personnel to ensure the trial is ethical and participant rights are protected. The federal government, medical institutions, and private industry (eg, pharmaceutical, biotech companies) commonly provide financial support for clinical trials.
Clinical Trial Phases
Many years of laboratory testing often is required before human volunteers become involved in a study. Pre-trial lab research helps to increase participant safety and study efficacy, which is paramount. 
A new clinical trial usually enrolls less than 100 participants (called Phase I). Depending on Phase I results, the trial may be continued and involve greater numbers of participants. 
A Phase II trial may involve up to 300 participants, and Phase III may include up to 3,000. 
Each phase of the study is considered a separate clinical trial. 
A Phase IV clinical trial is also called a post-marketing study. A Phase IV study is established when the drug, device, or product is available for consumer use.