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Clinical Trials: A Guide for Patients

What Is a Clinical Trial?

A clinical trial is a research program conducted with patients to evaluate a new medical treatment, drug, or device. The purpose of clinical trials is to find new and improved methods of treating, preventing, screening for, and diagnosing different diseases.

Clinical trials make it possible to apply the latest scientific and technological advances to patient care.

During a clinical trial, doctors use the best available treatment as a standard to evaluate new treatments. The new treatments are hoped to be at least as effective as -- or possibly more effective than -- current treatments.

New treatment options are first researched in the laboratory, where they are carefully studied in the test tube and in laboratory animals. Only the treatments most likely to work are further evaluated in a small group of humans prior to applying them in a larger clinical trial.

When a new medical treatment is studied for the first time in humans, scientists don't know exactly how it will work. With any new treatment, there are possible risks as well as benefits. Clinical trials help physicians discover the answers to these questions:

  • Is the treatment safe and effective?
  • How well does the treatment work?
  • Is the treatment potentially better than the treatments currently available?
  • What are the side effects and risks of the treatment?

Phases of a Clinical Trial

Clinical trials are conducted in phases, each designed to find out specific information. Each new phase of a clinical trial builds on information from previous stages.

Participants may be eligible for clinical trials in different phases, depending on their overall condition. Most clinical trial participants take part in phases III and IV.

What Are the Different Phases of a Clinical Trial?

  1. Phase I clinical trial. A new research treatment is given to a small number of participants and emphasizes safety. The researchers determine the best way to give the new treatment, find out the drug’s most frequent and serious side effects, and how much of it can be given safely.
  2. Phase II clinical trials. Determine the effect of a research treatment on the particular disease or condition being evaluated.
  3. Phase III clinical trials. Compare the new treatment with the standard treatment and study different populations and different dosages and combinations of drugs.
  4. Phase IV clinical trials. Apply the new treatment to general patient care (after FDA approval for marketing); for example, a new drug that was found effective in a clinical trial may be used together with other effective drugs to treat the particular disease or condition in a select group of patients.
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