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Health Risk Science -
Clinical studies

A clinical study also referred to as a clinical trial is a bio-medical or health-related research study in humans designed to assess the safety and effectiveness of drugs, devices, treatments, or preventive actions. All clinical studies need to follow a formal protocol approved by an Ethics Review Board responsible to assure the safety, rights and welfare of human subjects participating in such studies. All drugs approved for human use are tested in clinical trials beforehand.

Two groups are usually part of a clinical study. A control group is used as a standard for comparison. For example, this group could receive either a standard treatment or a placebo. The experimental group is composed of those participants who will receive the drug, device, treatment, or intervention under investigation.

Blinded studies are performed to reduce the likelihood of influencing the study results. A single-blinded study means the participants do not know if they are part of the experimental or control group. In a double-blinded study, neither the participants nor the researchers know who belongs to the experimental and control group.

An experimental drug or treatment is always tested in a clinical study as it is not yet commercially available or approved for marketing. In Canada, the authority falls with The Food and Drug Regulations provide to the Health Products and Food Branch (HPFB) of Health Canada to regulate the sale of drugs used in human clinical trials. In the United States, the Food and Drug Administration (FDA) is the U.S. agency responsible of approving a drug for marketing before it is used by the public. Information on clinical trials approved in the United States is available at

The Phases of a Clinical Trial
A clinical trial usually consists of four phases.

Phase 1 is the first step to investigating a new drug in human subjects. In a phase 1 study, investigators are interested to determine how the drug is metabolized in the human body and its interactions with the human body. They also provide evidence of side effects with increased dosage and early evidence of the biological effectiveness. Phase 2 is the first effectiveness studies of a drug tested in humans with the doses and schedule found to be safe in a Phase 1 study. The drug is tested with participants who have the disease or condition under investigation. They include a relatively small number of participants closely monitored for short-term side effects and risks and involve a control group.   Phase 3 studies are long-term investigations with up to several thousands participants intended to collect evidence of effectiveness and safety and evaluate overall benefit/risk ratio of the drug. The drug under investigation is then compared to the standard treatment. Phase 4 is intended for post-market surveillance once the drug has been made available to the public. Additional information can be gathered in the “real-world” with large-scale usage. Pharmacovigilance is an umbrella term used to describe the processes for monitoring and evaluating adverse drug reactions (ADRs) following the introducing of new drugs into the marketplace, and is a key component of effective drug regulation systems. Pharmacovigilance programs are useful to:

    • To monitor the effectiveness and safety of new and medically evolving treatments under real-life conditions post release.
    • To gather information about use in specific population groups notably children, pregnant women and the elderly.
    • To gather information on the efficacy and safety of chronic use of drugs in combination with other medicines.


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