A clinical trial is a prospective biomedical or behavioral research study of human subjects that is designed to answer specific questions about the biomedical or behavioral interventions (drugs, treatments, devices, or new ways of using known drugs, treatments or devices). Clinical trials are used to determine whether new biomedical or behavioral interventions are safe, efficacious and effective.
Biomedical clinical trials of an experimental drug, treatment, device or behavioral intervention may proceed through four phases:
- Phase I - Test a new biomedical intervention in a small group of people (e.g. 20-80) for the first time to determine efficacy and evaluate safety (e.g. determine a safe dosage range and identify side effects).
- Phase II - Study the biomedical or behavioral intervention in a large group of people, several hundred, to determine efficacy and further evaluate safety.
- Phase III – Study to determine efficacy of the biomedical or behavioral intervention in a larger group of people, from several hundred to several thousand by comparing the intervention to other standard or experimental interventions as well as to monitor adverse effects and to collect information that will allow the intervention to be used safely.
- Phase IV - Studies conducted after the intervention has been marketed. These studies are designed to monitor the effectiveness of the approved intervention in the general population and to collect information about any adverse effects associated with widespread use.