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How Do Clinical Trials Work? How Can They Improve Health Care?

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How Do Clinical Trials Work and How Can They Improve Health Care? Minerva Studio/Fotolia

A clinical trial is a research study used to test a new medicine, treatment or medical device to see if it is safe and effective before it is approved and released to the public.

To participate in a clinical trial, people must meet certain eligibility criteria to determine that they are suitable to take part.

Participants must be informed of risks and benefits of participating, though some risks may be unknown. They must sign a formal consent form before they can join to be part of the study.

It does not cost the participant any money to be part of a clinical trial, though there may be patient-care expenses that one’s health insurance won’t pay. The trial will last a few weeks to months.

There are several types of clinical trial protocols, depending on what is being tested, but the one for drug approval is outlined below.

Clinical drug trials are divided into four phases after the pre-clinical testing work has been completed.

Phase 1: Testing for safety

This is the first time the new drug or treatment is used on people. The group will have 20 to 80 volunteers and run for a short period of time. This phase tests a drug's safety and helps determine a therapeutic dose.

Phase 2: Determining effectiveness

This trial tests a larger group of participants, between 36 and 300, and lasts longer than the Phase 1 trial study. It also looks for side effects that people may experience with the drug.

Different population groups will be gathered and studied for their responses to the drug. The most effective dose will be determined, as will whether or not it is appropriate to be given along with other drugs.

Phase 3: Final determination of safety and effectiveness

If effectiveness is proven in Phase 2, then this trial tests the new medicine against standard treatments that already exist to treat a particular condition. This group is much larger, with between 300 and 3,000 participants.

These studies are usually performed as controlled studies. All the patients are in a particular stage of their disease. The patients are picked at random for each group. Some are put in the “control” group, receiving a placebo and/or some other drug. The rest are in the test group, receiving the actual drug being tested.

In a single-blind study, the patients do not know which group they are in, but the researchers know. In a double-blind study, neither the patients nor the researchers know who is in each group until the end of the study.

“Most cancer clinical trials do not use placebos unless they are given along with an active drug. It’s unethical to give someone a placebo if it would deny the person a chance to get a drug that’s known to work,” noted the American Cancer Society.

At the end of Phase 3 testing, the drug sponsor will file a New Drug Application, also called an NDA, in order to request that the FDA consider approving a new drug for sale and use in the United States.

According to the U.S. Department of Veteran Affairs, “It usually takes about 10 years for a drug to be developed and approved for prescription. Even after a drug has been successful in a Phase III trial, it still may take six to 12 months before that drug is approved for prescription.”

Phase 4: Observation study after drug is available for sale

This phase is used after the drug is approved and available by prescription. It is used to determine appropriate doses or further study side effects. The testing group may be over 1,000 patients.

This phase can watch for long-term side effects of the drug and detect any additional serious side effects that may occur.

Clinical trials provide a closely monitored and supported method for us to obtain new drugs or therapies to treat a variety of conditions. They also allow some to have access to the drugs early since it take so many years to actually bring a drug to market.


What are clinical trials? How do clinical trials work? Medical News Today (MNT). Retrieved Sept. 23, 2015.

How do clinical trials work? U.S. Department of Veterans Affairs. Retrieved Sept. 23, 2015.

Clinical Trials: What You Need to Know. American Cancer Society. Retrieved Sept. 23, 2015.

What are the Phases of Clinical Trials? The University of Texas MD Anderson Cancer Center. Retrieved Sept. 23, 2015.

Michele is an R.N. freelance writer with a special interest in woman’s health care and quality of care issues.

Edited by Jody Smith

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We value and respect our HERWriters' experiences, but everyone is different. Many of our writers are speaking from personal experience, and what's worked for them may not work for you. Their articles are not a substitute for medical advice, although we hope you can gain knowledge from their insight.