Clinical Trials: What You Need to Know

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Phase IV clinical trials: What else do we need to know?

Drugs approved in phase III trials are often watched over a long period of time in phase IV studies. Even after testing a new medicine on thousands of people, the full effects of the treatment may not be known. Some questions may still need to be answered. For example, a drug may get FDA approval because it was shown to reduce the risk of cancer recurrence. But does this mean that those who get it are more likely to live longer? Are there rare side effects that haven’t been seen yet, or side effects that only show up after a person has taken the drug for a long time? These types of questions may take many years to answer, and are often addressed in phase IV clinical trials.

Key points of phase IV clinical trials:

  • Phase IV studies look at drugs that have already been approved by the FDA. The drugs are available for doctors to prescribe for patients, but phase IV studies are needed to answer important questions.
  • May involve at most, a few tens of thousands of people.
  • The safest type of clinical trial because the treatment has already been studied a lot and used in possibly millions of people. Phase IV is looking at safety over time.
  • These studies may also look at other aspects of the treatment, such as quality of life or cost effectiveness.

You can get the drugs used in a phase IV trial without enrolling in a study. And the care you would get in a phase IV study is very much like the care you could expect if you were to get the treatment outside of a clinical trial. But in phase IV studies you are helping researchers learn more about the treatment and doing a service to future patients.


Last Medical Review: 09/25/2014
Last Revised: 10/31/2014