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Types of clinical trials

by Peter P. Rowell last modified Jan 31, 2008 01:14 PM

The Clinical Trials Process - What you need to know

Every medical breakthrough approved for use in patients has been through the four phases of the clinical trials process, as defined by the National Institutes of Health.

Once researchers test new therapies or procedures in the laboratory and get promising results, they begin planning Phase 1 clinical trials. New therapies are tested on people only after laboratory and animal studies show promising results.

Phase 1

A Phase 1 clinical trial is directly built upon basic and animal research and is primarily used to test the safety of a therapy and to estimate possible usefulness in a few human subjects.

Phase 2

A Phase 2 clinical trial usually involves many subjects at several different centers and is used to test safety and efficacy on a broader scale and to determine the best methodology for the bigger Phase 3 clinical trial to come.

Phase 3

A Phase 3 clinical trial often involves many centers and sometimes several hundred subjects. The trial usually has two patient groups who receive different treatments, but all other standard care is the same. Many Phase 3 trials are called double-blind, randomized clinical trials. Double-blind means that neither the subjects nor the doctors treating the subjects and determining the response to the therapy know which treatment a subject receives. Randomization refers to the placing of subjects into one of the treatment groups in a way that can't be predicted by the patients or investigators. These clinical trials usually involve many investigators and take many years to complete.

Most treatments for general use come out of Phase 3 clinical trials. After one or more phase 3 trials are finished, and if the results are positive for the treatment, the investigators can petition the FDA for government approval to use the drug or procedure to treat patients.

Phase 4

Sometimes Phase 4 clinical trials are conducted after a product is already approved and on the market to find out more about the treatment's long-term risks, benefits, and optimal use, or to test the product in different populations of people, such as children.

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