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“PHASES” of Pharmaceutical Trials Defined

For the benefit of news readers on the PDF website, we are providing here a brief explanation of the series of trials that a pharmaceutical agent must go through from its initial discovery (patent application) to its release for general use (FDA approval).

These trials are in three main categories, or phases.

  • In Phase I, the compound is tested in small trials of healthy individuals for safety and speed of metabolism, following extensive animal studies. (The animal studies often continue during the human trials.)
  • In Phase II, studies are designed to define still further the safety of the drugs. Such studies may be “open-label” (where individuals taking part in the trial know what is being tested) and small. Somewhat later, but still in Phase II, studies may be larger ‘blinded’ trials, in which neither the subjects nor the medical professionals know who is receiving the active drug and who is receiving a non-active substance known as a “placebo”.
  • Phase III trials are more disease-specific and are designed to expand knowledge of the effectiveness of an agent compared with other standard drugs already on the market. They tend to run over longer time periods and with a still larger population.
  • These studies, if successful, lead to applications for FDA approval. Once approved, some pharmaceuticals may be further tested in Phase IV trials, especially when earlier trials revealed that some unexpected benefits that might help patients with other disorders.

Source Date: Feb 10 2003