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Terminology

Clinical trial

A research study conducted to answer specific questions, usually on the safety and effectiveness of a particular treatment.

In Phase I trials, researchers test a new drug or treatment in a small group of people (20-80) for the first time to evaluate its safety, determine a safe dosage range, and identify side effects.

In Phase II trials, the study drug or treatment is given to a larger group of people (100-300) to see if it is effective and to further evaluate its safety.

In Phase III trials, the study drug or treatment is given to large groups of people (1,000-3,000) to confirm its effectiveness, monitor side effects, compare it to commonly used treatments, and collect information that will allow the drug or treatment to be used safely.

In Phase IV trials, post-marketing studies delineate additional information including the drug's risks, benefits, and optimal use.

Source: Resources page at Clinicaltrials.gov Website (new window).