Email this pageWhat are the phases of a clinical trial?
There are four phases of clinical trials. Each phase has a different purpose and provides researchers with important information for the following phases.
- Phase I Trials help evaluate the safety, side effects and proper dosage range for a new drug or treatment. In Phase I, from 20-80 people are involved.
- Phase II Trials typically involve 100-300 people. In this phase, researchers begin to study the effectiveness of the new drug or treatment. Its safety will also be further evaluated.
- Phase III Trials expand to a much larger group—from 1,000 to 3,000 people. Researchers look closely at how the new approach compares with the best drugs or treatments currently available.
- Phase IV Trials take place after a new drug or treatment has received permission to be sold. Researchers watch for rare side effects, study interactions with other drugs, consider other uses for the new drug or treatment and examine how it works in select populations.
