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About Clinical Trials

Introduction to Clinical Trials

Choosing to participate in a clinical trial is an important personal decision. The following frequently asked questions provide detailed information about clinical trials. In addition, it is often helpful to talk to a physician, family members or friends about deciding to join a trial. After identifying some trial options, the next step is to contact the study research staff and ask questions about specific trials.

What is a clinical trial?

Clinical trials are a means of developing new medicines, devices or procedures for the purpose of gaining medical knowledge relevant to the prevention, detection, diagnosis, control and treatment of medical diseases and conditions. More specifically, clinical trials are scientific studies designed to evaluate one or more groups of subjects, using one or more types of interventions.

The predominant intervention studied in clinical research is medicine. Consequently, experimental drugs are the focus of this website.

Clinical trials are categorized into five successive phases. Each new phase is designed to build on information discovered from previous phases.

The Preclinical phase occurs before the first phase of human testing. During the Preclinical phase, a drug is developed and then evaluated in cells and animals to see its potential effect on the human body. The development of a medication can take up to 18 years. The process of animal testing can take between one and one-half to four years.

If a drug shows promise in the Preclinical phase, a pharmaceutical company can request permission from the U.S. Food and Drug Administration (FDA) to begin testing in humans. This is called an Investigational New Drug application (IND).

Since larger numbers of patients receive a treatment in phase-2 studies than in phase-1 studies, there is a greater chance to observe and compile side effect information. Subjects in a phase-2 trial may benefit from their participation if they receive an active treatment. Approximately 33 percent of experimental drugs which pass phases 1 and 2 will go on to phase 3.

Why participate in a clinical trial?

Participants in clinical trials can play a more active role in their own health care, gain access to new research treatments before they are widely available and help others by contributing to medical research.

Who can participate in a clinical trial?

All clinical trials have guidelines about who can participate. Using inclusion/exclusion criteria is an important principle of medical research that helps to produce reliable results. The factors that allow someone to participate in a clinical trial are called "inclusion criteria" and those that disallow someone from participating are called "exclusion criteria."

These criteria are based on such factors as age, gender, the type and stage of a disease, previous treatment history and other medical conditions. Before joining a clinical trial, a participant must qualify for the study. Some research studies seek participants with illnesses or conditions to be studied in the clinical trial, while others need healthy participants.

It is important to note that inclusion and exclusion criteria are not used to reject people personally. Instead, the criteria are used to identify appropriate participants and keep them safe. The criteria help ensure that researchers will be able to answer the questions they plan to study.

What happens during a clinical trial?

The clinical trial process depends on the kind of trial being conducted (See What are the different types of clinical trials?) The clinical trial team includes doctors and nurses as well as social workers and other health care professionals. They check the health of the participant at the beginning of the trial, give specific instructions for participating in the trial, monitor the participant carefully during the trial and stay in touch after the trial is completed.

Some clinical trials involve more tests and doctor visits than the participant would normally have for an illness or condition. For all types of trials, the participant works with a research team. Clinical trial participation is most successful when the protocol is carefully followed and there is frequent contact with the research staff.

What are the benefits and risks of participating in a clinical trial?

Clinical trials that are well designed and well executed are the best approach for eligible participants to:

  • Play an active role in their own health care.
  • Gain access to new research treatments before they are widely available.
  • Obtain expert medical care at leading health care facilities during the trial.
  • Help others by contributing to medical research.


  • There are risks to clinical trials.
  • There may be unpleasant, serious or even life-threatening side effects to treatment.
  • The treatment may not be effective for the participant.
  • The protocol may require more of their time and attention than would a non-protocol treatment, including trips to the study site, more treatments, hospital stays or complex dosage requirements.

Clinical Research Terminology

Adverse Event = An unfavorable and unintended medical occurrence in a subject who is administered a medicinal product which is not necessarily the cause of that occurrence. A subject may withdraw or be withdrawn from a research study if an adverse event becomes too severe.

Adverse Drug Reaction = An unfavorable and unintended medical occurrence in a subject who is administered a medicinal product which is the most probable cause of that occurrences. A subject may withdraw or be withdrawn from a research study if an adverse drug reaction becomes too severe.

Double-Blind Study = A study in which neither the subject nor the investigator knows which treatment a subject is receiving. However if medically necessary, the study pharmacist can reveal a subject's "blind."

Control Group = A group of subjects that receives no treatment, a standard treatment or a placebo.

Healthy Volunteer = A volunteer subject with no known significant health problems who participates in research to test a new drug, device, or intervention. Research with healthy volunteers is designed to develop new knowledge, not to provide direct benefit to study participants. Healthy volunteers in phase-1 trials serve as controls for patient groups in later phase trials.

Informed Consent = A process that involves: 1) giving a subject adequate information in straightforward language regarding study-related procedures, risks and benefits in both oral and written form, providing the subject with the opportunity to consider all other options besides participation; 2) responding to the subject's questions; 3) ensuring that the subject comprehends all aspects of participation; and 4) obtaining the subject's voluntary, signed consent form. If the subject is considered to be a minor or incompetent, a legal representative should sign on his or her behalf.

Institutional Review Board = An independent group of medical and non-medical members whose responsibility is review research protocols to ensure the protection of the rights of human subjects. The IRB enforces strict rules for clinical trials, which are monitored nationwide by the FDA and the National Institutes of Health (NIH).

Open-Label Study = A study in which both subject and investigator know which treatment a subject is receiving (opposite of double-blind).

Patient Volunteer = A volunteer subject with a health problem who participates in research to better understand, diagnose, treat or cure his or her disease or condition. Research procedures may or may not benefit the volunteer patient.

Protocol = A written document that describes the objectives, design and methods of a study.

Placebo = A harmless, inactive substance designed to look like the active treatment. If a placebo is part of a study, you will always be informed of this fact in the consent form.

Randomization = The process of assigning trial subjects to treatment or control groups by random allocation (chance, not choice) in order to reduce potential bias in the study results.

Single-Blind Study = A study in which only the subject is unaware of the treatment received.

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