Clinical Trial Phase descriptions

Phase I: Researchers test a new drug or treatment in a small group of people (20-80) for the first time to evaluate its safety, determine a safe dosage range, and identify side effects.

Phase II: The study drug or treatment is given to a larger group of people (100-300) to see if it is effective and to further evaluate its safety.

Phase III: The study drug or treatment is given to large groups of people (1,000-3,000) to confirm its effectiveness, monitor side effects, compare it to commonly used treatments, and collect information that will ensure safe usage.

Phase IV: These studies are done after the drug or treatment has been marketed. The testing continues to collect information about the effect of the drug or treatment in various populations and determine any side effects from long-term use.