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Participate in Clinical Studies
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Phases of a Clinical Trial
A clinical trial may usually be categorized as falling into one of four stages or "phases."
This is the first experience using the new drug or treatment in humans. Both healthy adult
participants and those adults and children with the disease being studied may be enrolled.
Phase 1 studies are designed to determine how the drug is broken down in the human body and
how it interacts with the human body. Phase 1 studies test the safety and possible side effects
of the new therapy. Phase 1 studies may also provide the first evidence of effectiveness.
Researchers use information from Phase 1 studies to design Phase 2 studies. Phase 1 studies
typically enroll only a small number of people, sometimes as few as a dozen.
These are the first effectiveness studies of a drug in humans. Taking the drug at the doses and
on the schedule found to be safe in Phase 1 trials, researchers administer the drug to
participants with the disease or condition of interest. During Phase 2, researchers collect
additional safety and effectiveness data, further study the side effects and risks, and collect
additional information about the proper dose and dosing schedule. Phase 2 studies typically
involve control
groups, are closely monitored, and are conducted in a relatively small number of
participants, usually not more than several hundred participants.
These studies are expanded, longer-term research studies, performed after Phase 1 and Phase 2
studies have shown some evidence of both safety and effectiveness. Phase 3 studies are intended
to gather additional information about effectiveness and safety needed to evaluate the overall
benefit/risk relationship of the study drug/treatment as compared to the current standard
therapies for specific diseases/conditions. Researchers collect additional information about
drug or treatment-related side effects, including the less common side effects. Several hundred
to several thousand participants may be enrolled. At the conclusion of a properly designed
Phase 3 trial, the new drug or treatment will be found to be inferior, equivalent, or superior
to the standard treatment.
The intent of these "post-marketing surveillance" studies is to learn more about the drug after
it has been approved by the U.S.
Food and Drug Administration. In Phase 4 studies, researchers gather additional information
about an approved drug's risks, benefits, and best uses associated with large-scale usage in
"real-life conditions."
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