An 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 participate in a clinical trial.


Table of Contents

·         What is a clinical trial

·         What are the phases of clinical trials

·         Where do the ideas for clinical trials come from

·         Why participate in a clinical trial

·         Who can participate in a clinical trial

·         What is informed consent

·         What should people consider before participating in a clinical trial

·         Who funds clinical trials


What is a clinical trial?

Health Canada defines clinical trial as an investigation in respect of a drug or treatment for use in humans that involves human participants and that is intended to discover or verify the clinical, pharmacological (preparation, use and effectiveness), or pharmacodynamic (breakdown of drugs within the body) effects of the drug or treatment, identify any adverse events (side effects) in respect of the drug or treatment, study the absorption, distribution, metabolism and excretion of the drug, or ascertain the safety or efficacy (effectiveness) of the drug.  Clinical trials are regulated by governing bodies in the country where the clinical trial is being conducted (e.g. Health Canada in Canada and the Food and Drug Administration in the U.S.A.). 


New drugs, a new indication for a current drug, new medical devices, and new approaches to current therapies must undergo clinical trials to assess their efficacy (effectiveness) and safety before being approved for use in the population.  Clinical trials related to new drugs, new indications for current approved drugs, medical devices and natural health products must all undergo review and approval by Health Canada before being made available to the public.  Clinical trials provide the necessary documentation to allow this approval process to take place.


Physicians, nurses, and health care professionals involved in clinical trials are required to adhere to national and local regulations, good clinical practice guidelines and ethical codes of conduct.


All research that involves living human participants must be reviewed and approved by a Research Ethics Board (REB) at the hospital or clinic where the research is being conducted before the research is started.  It is the responsibility of the REB to ensure the protection of the rights, safety and well-being of human participants involved in research by reviewing and approving the clinical trial, the suitability of the Investigator (physician leading the clinical trial), facilities and the methods and materials to be used in obtaining and documenting informed consent.


Trials can take place in a variety of locations, such as hospitals, universities, doctors' offices, or community clinics.

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What are the phases of clinical trials?

Clinical trials are classified and conducted in phases. Each phase has a different purpose and helps researchers answer different questions.  Health Canada defines each phase as follows:

Phase I trials

In Phase I trials, researchers conduct initial safety studies on a new drug or treatment.  This includes the first administration of the drug or treatment into humans.  Phase I trials are usually conducted in healthy volunteers.

Phase II trials

In Phase II trials, researchers evaluate the efficacy (effectiveness) of the drug or treatment in patients with the medical condition to be treated, diagnosed or prevented and to evaluate the safety of the drug or treatment by determining the side effects and risks associated with the drug or treatment.  Phase II trials generally involve less than 100 participants.

Phase III trials

Phase III trials are conducted after preliminary evidence suggesting efficacy (effectiveness) of the drug or treatment has been demonstrated.  Efficacy (effectiveness) and safety results are taken from the Phase II trial.  Phase III trials often compare commonly used treatments with the study drug or treatment and generally enroll a large group of patients (> 1,000).

Phase IV trials

Phase IV trials are performed after the drug or treatment has been authorized by the regulator (approved by Health Canada) for the market and related to the authorized indication.

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Where do the ideas for clinical trials come from?

Ideas for clinical trials usually come from researchers.  The first step is the development of new drugs or new uses for existing drugs, treatments and procedures.  The first step is to test these in the laboratory and in animals.  The drugs, treatments and procedures with the most promising results, established from the laboratory and animal studies, move into clinical trials that involve human participants.  During a trial, more and more information is documented about the new drug, treatment and procedure, including its benefits and risks, and the optimal approach to treatment.

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Why participate in a clinical trial?

Participants in clinical trials gain access to new research treatments before they are widely available, can play a vital role in their own treatment, and contribute to helping others by being involved in research.

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Who can participate in a clinical trial?

All clinical trials have requirements about who can participate. Using specific criteria to include or exclude participants is important to ensure that the drug or treatment is studied in individuals for whom it is intended (patient population).  These criteria may be based on such factors as age, gender, the type and stage of a disease, previous treatment history, and other medical conditions. It is important to note that inclusion and exclusion criteria are not used to reject people personally.  Instead, the criteria are used to identify potential participants who will most benefit from the drug and/or treatment with the least amount of side effects.    


While in a clinical trial, participants are seen regularly by the research staff to monitor their health and to determine the safety and effectiveness of their treatment

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What is informed consent?

Informed consent is a process by which the trial participant voluntarily confirms his or her willingness to participate in a particular clinical trial, after having been informed of all aspects of the trial that relate to their participation.  Doctors and nurses involved in the trial will explain the details of the clinical trial, outlining the potential benefits and the risks associated with the trial, the duration of the trial, tests and procedures that may be required, follow-up and confidentiality aspects.  Potential participants should ask questions and be given time to consider their participation.  Informed consent is documented by means of a written, signed and dated consent form.  The participant has the right to withdraw consent at any time.

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What should people consider before participating in a clinical trial?

People should know as much as possible about the clinical trial and feel comfortable asking the members of the health care team questions.  Potential study participants should be aware of the treatment that will be provided, their time commitment, the length of follow-up and the potential benefits and risks associated with the clinical trial. The following questions might be helpful for the participant to discuss with the health care team.  The answers to these questions should be presented and discussed with you before you agree to participate in a clinical trial.  These items should also be outlined in the informed consent document.

o        What is the purpose of the clinical trial?

o        How many people will take part in the clinical trial?

o        What types of tests, procedures, and treatments are involved?  

o        What are the possible risks, side effects, and benefits and how does this compare with current treatment?

o        How might this trial affect my daily life?

o        How long will the trial last?

o        Will hospitalization be required?

o        Who will pay for the experimental treatment?

o        Will I be reimbursed for other expenses?

o        Is follow up required?  How often will I need to come to the hospital or clinic?

o        Will the results of the clinical trial be provided to me?

o        Who will be in charge of my care?

o        Why am I being asked to complete questionnaires?

o        How is my confidentiality protected?

o        Can I withdraw from the trial after I have provided consent and started treatment?

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Who funds clinical trials?

Clinical trials are funded by a variety of organizations and companies.  These include the National Cancer Institute of Canada (NCIC), the Canadian Institute for Health Research (CIHR), disease specific groups such as the Canadian Breast Cancer Research Alliance or the Heart and Stroke Foundation.  The Ministry of Health in each Canadian province also provides funding for new technologies.  Pharmaceutical companies, and foundations such as the Canadian Cancer Society also fund clinical trials. 

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