Four Phases of Clinical Trials
Clinical Trials are conducted in four phases, as defined by the National Institutes of Health:
Phase I - Researchers test a new drug or treatment in a small group of volunteers (20-80) for the first time to evaluate its safety, determine a safe dosage range and identify side effects. When results from Phase I are promising (meaning the benefits appear to outweigh the risks), then Phase II Trials may begin.
Phase II - The study drug or treatment is given to a larger group of volunteers (100 - 300) to see if it is effective and to further evaluate its safety.
Phase III - The study drug or treatment is given to large groups of volunteers (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.
Phase IV - Post marketing studies outline additional information including the drug's risks, benefits and optimal use.
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