What is a Clinical Trial?

Understanding the research process and how new treatments are developed

Definition and Purpose

Clinical trials are research studies performed in people that are aimed at evaluating a medical, surgical, or behavioral intervention. They are the primary way that researchers find out if a new treatment, like a new drug or diet or medical device (for example, a pacemaker) is safe and effective in people.

Clinical trials are carefully designed to answer specific research questions related to the effectiveness and safety of a treatment or intervention. They help researchers find better ways to prevent, diagnose, or treat disease.

Types of Clinical Trials

  • Treatment trials test new treatments, such as a new drug, surgery, or radiation therapy.
  • Prevention trials look for better ways to prevent disease in people who have never had the disease or to prevent a disease from returning.
  • Diagnostic trials are conducted to find better tests or procedures for diagnosing a particular disease or condition.
  • Screening trials test the best way to detect certain diseases or health conditions.
  • Quality of life trials (or supportive care trials) explore ways to improve comfort and quality of life for people with chronic illness.

Phases of Clinical Trials

Clinical trials are conducted in a series of steps called "phases." Each phase has a different purpose and helps researchers answer different questions:

Phase I

Researchers test a new 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.

Phase II

The drug or treatment is given to a larger group of people (100-300) to see if it is effective and to further evaluate its safety.

Phase III

The drug or 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.

Phase IV

Studies are done after the drug or treatment has been marketed to gather information on the drug's effect in various populations and any side effects associated with long-term use.

Clinical Trial Protocols

All clinical trials have protocols, which are carefully designed study plans that safeguard the health of the participants while answering specific research questions. A protocol describes:

  • Who is eligible to participate in the trial
  • Details about tests, procedures, medications, and dosages
  • The length of the study and what information will be collected

The protocol is reviewed and approved by an Institutional Review Board (IRB) before the study begins, to ensure that the research is ethical and that participants' rights are protected.

How to Participate

If you're interested in participating in a clinical trial, you can:

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