There are three different phases of clinical trials with different purposes, beginning with the first use of a drug or treatment on humans, and finishing with approval for general public use by the FDA. These include:
Phase 1 Clinical Trials – Is the Treatment Safe?Phase 1 trials are the first tests done on humans for an experimental medication or treatment. They usually involve only a small number of people and are designed to see if a treatment is safe.
Phase 2 Clinical Trials – Does the Treatment Work?After a drug or treatment is found to be relatively safe, it is tested in a phase 2 trial to see if it is effective. Since a larger number of individuals are enrolled in these studies, further information is obtained about safety as well.
Phase 3 Clinical Trials – Does the Treatment Work Better Than the Standard Treatment?Once a medication or treatment is felt to be relatively safe and effective, it is studied in a phase 3 trial to see if it works better than, or has fewer side effects than, the standard treatments available. Phase 3 trials are usually conducted on hundreds to thousands of individuals, and are usually “double-blind” studies; meaning that neither the patient nor the investigator knows which treatment is being used. If the experimental treatment is found to be either superior or inferior to the standard treatment, these studies are usually stopped early to allow individuals to receive the best treatment possible.
There are also phase 4 clinical trials. After a drug has been approved for general use, a phase 4 trial may be done to look at the safety of a drug or procedure over time, or to look at other uses for the drug.Further Reading:
National Library of Medicine. FAQ. ClinicalTrials.gov – Clinical Trial Phases. Updated 04/18/08. http://www.nlm.nih.gov/services/ctphases.html