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Current Clinical Trials (Last updated : 7 Mar 2011)

Clinical trials Clinical trials of experimental drugs are conducted in four phases. The trials at each phase have a different purpose and help scientists answer different questions:

Phase I:

In Phase I trials, researchers test an experimental 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. [1] The Phase I of a clinical trial design can be open, meaning that both researcher and subject may know the details of the treatment. Phase I studies can also be baseline controlled: there is an assessment of the volunteer before and after treatment. Randomisation and blinding may also be used. In this case, there is a random allocation of the treatment, without the researcher and/or the subject knowing what treatment is being administered, which lead to more accurate results. [2]

Phase II:

In Phase II trials, the experimental 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. [1]

While early studies of Phase II may include be baseline controlled, later studies of Phase II are usually randomized with a placebo control, to evaluate the efficacy of the new drug and its safety under specific conditions or indications.

In Phase II, the therapy or drug is usually administered on a relatively uniform patient population, and groups are larger than those of Phase I. Subjects are closely monitored and information collected is important to determine the doses and treatment indications that will be used during Phase III. [2]

Phase III:

In Phase III trials, the experimental 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 experimental drug or treatment to be used safely [1]. Additional Phase III studies may be used to research the dose-response relationship or the drug's use in wider populations, in different stages of disease, or in combination with another drug.

Phase III studies are done on large group patients and are randomized controlled multicenter trials. The size and the relatively lengthy duration of Phase III trials make them notably expensive and time-consuming. [2]

Phase IV:

In Phase IV trials, post marketing studies delineate additional information including the drug's risks, benefits, and optimal use. [1]

Clinical trial Phase IV can be used to refine the dosing recommendation of a drug or to identify rare side effects. Mortality and morbidity or epidemiological studies are other examples of a clinical trial Phase IV studies. Some Phase IV studies have lead to the findings of harmful side effects, and the discontinuation or use restriction of some drugs. [2]

Reference:
[1] http://clinicaltrials.gov/ct2/info/understand#Q01
[2] http://www.clinical-trials-info.com/phases/

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