Clinical Trial - Phases


Clinical trials involving new drugs are commonly classified into four phases. Each phase of the drug approval process is treated as a separate clinical trial. The drug-development process will normally proceed through all four phases over many years. If the drug successfully passes through Phases 1, 2, and 3, it will usually be approved by the national regulatory authority for use in the general population.

  • Phase 1: Screening for safety
  • Phase 2: Establishing the testing protocol
  • Phase 3: Final testing
  • Phase 4: Postapproval studies

Each phase has a different purpose and helps scientists answer a different question:

In Phase 1 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.

In Phase 2 trials, the experimental 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 3 trials, the 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 it to be used safely.

In Phase 4 trials, postmarketing studies delineate additional information, including the treatment's risks, benefits, and optimal use.

Before pharmaceutical companies start clinical trials on a drug, they conduct extensive preclinical studies.

Read more about this topic:  Clinical Trial

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Famous quotes containing the word phases:

    That man is to be pitied who cannot enjoy social intercourse without eating and drinking. The lowest orders, it is true, cannot imagine a cheerful assembly without the attractions of the table, and this reflection alone should induce all who aim at intellectual culture to endeavor to avoid placing the choicest phases of social life on such a basis.
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    But parents can be understanding and accept the more difficult stages as necessary times of growth for the child. Parents can appreciate the fact that these phases are not easy for the child to live through either; rapid growth times are hard on a child. Perhaps it’s a small comfort to know that the harder-to-live-with stages do alternate with the calmer times,so parents can count on getting periodic breaks.
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    This socialism will develop in all its phases until it reaches its own extremes and absurdities. Then once again a cry of denial will break from the titanic chest of the revolutionary minority and again a mortal struggle will begin, in which socialism will play the role of contemporary conservatism and will be overwhelmed in the subsequent revolution, as yet unknown to us.
    Alexander Herzen (1812–1870)