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Clinical Trial Phases

For a treatment to become standard, it must first go through 3 or 4 clinical trial phases. The early phases make sure the treatment is safe. Later phases show if it works better than the standard treatment.

Researchers take many years testing investigational drugs in the laboratory before the drug can be tested in humans. When the initial laboratory research is successful the drug can be moved into testing in humans through a clinical trial. All phases of clinical trials are monitored closely by the Food and Drug Administration (FDA).

The table below provides an overview of the four phases of clinical trials, general number of volunteers needed for each phase, and a description of the goal of each phase.

Click here to return to the clinical trials page.
Click here to read about randomization in clinical trials.