Clinical trials are research projects that are designed to determine if an intervention will improve a person’s health.

In 2014, the National Institutes of Health (NIH) defined a clinical trial as “a research study in which one or more human subjects are prospectively assigned to one or more interventions (which may include placebo or other control) to evaluate the effects of those interventions on health-related biomedical or behavioral outcomes.”

The U.S. Department of Health and Human Services and NIH have created specific policies to regulate clinical trials.  Clinical trials are classified into different phases.  Each phase has a different purpose and helps researchers answer different questions.

• Phase I trials: Researchers test an experimental drug or treatment in a small group of people (20–80) for the first time. The purpose is to evaluate its safety and identify side effects.
• Phase II trials: The experimental drug or treatment is administered to a larger group of people (100–300) to determine its effectiveness and to further evaluate its safety.
• Phase III trials: The experimental drug or treatment is administered to large groups of people (1,000–3,000) to confirm its effectiveness, monitor side effects, compare it with standard or equivalent treatments, and collect information that will allow the experimental drug or treatment to be used safely.
• Phase IV trials: After a drug is approved by the FDA and made available to the public, researchers track its safety, seeking more information about a drug or treatment’s risks, benefits, and optimal use.

Questions to ask
https://www.nih.gov/health-information/nih-clinical-research-trials-you/basics#5