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What is a Clinical Trial?

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What Is a Clinical Trial?

Clinical trials, also known as clinical studies, are scientific studies in which people help doctors find ways to improve health and health care. Many of today's treatments for illness are based on the results of past clinical trials. In clinical trials, people take new medicines or treatments that have been found to be helpful and safe in test tubes and in animals. Scientists who conduct these studies want to learn:

  • Does the medicine (often called a study agent) prevent or treat the illness in humans?
  • How safe is it for humans to take the study agent?


Who Can Participate?

Clinical trials try to enroll people who are alike in certain ways, depending on the study's purpose. The study's protocol tells who can join the study and spells out the characteristics that people should have. These are called eligibility criteria. They may include age, gender, general health, and risk factors.

Eligibility criteria are a key part of medical research. They help produce results we can trust. And after those results are known, the information can help doctors find out who will be helped by the approach being studied if it's shown to work. For example, a new drug might not work for people with one type of risk factor, or it may work better for men than for women.

Eligibility criteria also help protect you. They help make sure that if you are likely to be harmed by something in the study, you are not exposed to that risk.

Testing in humans is permitted only if a person volunteers for participation. The person is informed of all the risks and benefits of taking part in the study, including details about the study approach and any tests that may be performed. When a person decides to participate, he or she signs a consent form. This process is called informed consent, and it lasts as long as the person is in the study. In other words, a volunteer can change his or her mind and leave a study at any time.


Studies Seeking Patients

The National Institutes of Health has developed a consumer-friendly database,, to provide patients, family members, and members of the public current information about clinical research studies. You can search the entire database or you can go directly to a list of NIDCD clinical studies.


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