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What is a Clinical Trial?

A clinical trial is a research study that is done to find out if medical treatments can improve people’s health. A medical treatment can be a drug, medical device, medical procedure or a change in a person’s behavior such as diet or exercise. People who take part in clinical trials are volunteers. They are also called “participants.” 

Researcher testing sample

Why is it important to participate?

Clinical trials cannot be done without the people who choose to participate. Some reasons that people choose to participate in clinical trials are to play a more active role in their own health care, gain access to new medical treatments before they are available to the wider public and help others by contributing to medical research that finds new or better treatments for people with illnesses and diseases.

How are clinical trials conducted?

Before a clinical trial can start, the research team creates a research plan. The research plan is also called the “protocol”. The protocol describes:

  • the length of the study
  • the rules about who may or may not participate in the trial
  • the schedule of tests, procedures, medications, and dosages
  • the information the researchers want to collect about the treatment

A research team is assigned at each clinical trial location. The research team usually includes doctors, nurses and other health care professionals.

The protocol is usually reviewed by an independent group of scientists and other professionals to help make sure that the study will be safe for the people with the disease or condition to participate in. Once the protocol is approved, the clinical trial can begin and participants can join.

During a clinical trial, the participants receive treatments and have tests done according to the protocol. Some trials compare a new treatment to a standard one that is already available. Other trials compare a treatment to a placebo. A placebo looks like a treatment but does not have any medicine in it. Some trials just look at a treatment without any comparisons. The research team collects information from the participants during the trial. This information helps them find out how safe and effective the treatments were in the trial.

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

What are clinical phases?

Clinical trials are conducted in steps that are called “phases”. There are four phases of trials. Each phase has a different purpose and helps researchers answer different questions:

  1. In Phase I trials, 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.
  2. In Phase II trials, the study 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.
  3. In Phase III trials, the study 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 the drug or treatment to be used safely.
  4. In Phase IV trials, post marketing studies delineate additional information including the drug's risks, benefits, and optimal use.