Understanding Clinical Trials
Last updated: November 2023
A clinical trial is a type of research. Research is the process scientists use to explain how our bodies work or why our bodies stop working well. Clinical trials are studies that help doctors learn whether a new drug, device, surgery, diet change, treatment method, or type of education is safe and works well in humans.1-3
Clinical trials lead to better healthcare and longer, healthier lives.
Types of clinical trials
There are several types of clinical trials. These trials can be described by the type or phase of research, such as:1
Behavioral trials look at whether a change in how a person behaves improves their health. The change might be in diet, exercise, social support, or mental health.
Diagnostic trials look at how a disease is diagnosed. These studies try to find out whether new tests are more accurate or faster at finding a health problem.
Interventional study is another name for a clinical trial. A clinical trial tests, or tries out, whether an intervention works. An intervention may be a new drug, device, surgery, test, or activity.
Observational studies do not change or test treatment, but follow up to see how well a new treatment is working. A questionnaire or a survey that asks questions about a new drug or the side effects of a surgery are examples of observational studies.
Prevention trials test whether new drugs, vaccines, or lifestyle changes prevent a disease from occuring for the first time or from returning.
Quality-of-life trials look at ways to improve the quality of life of people with a certain illness.
Screening trials test new ways to find diseases.
Treatment trials test new drugs, devices, surgeries, and other treatments to see whether they are safe and how well they work. These new treatments may also be compared with older treatments, a placebo, or combined with other treatments to see which works the best.
Clinical trial phases
The process to approve a treatment for use in humans can take years. Many new treatments are tested first in a lab, sometimes on animals other than humans. If the treatment looks promising, the treatment will then move on to tests on humans. This testing takes place in stages, and in the U.S. must follow rules laid down by the Food and Drug Administration.
Clinical trials run in 4 phases or stages:1
- Phase 1: A very small group of people take a new drug or device for the first time to look at safety, dosage range, and side effects. Less than 25 people may be involved in a Phase I trial.
- Phase 2: A larger group takes the drug to see how well it works and if it is still safe. It varies, but a phase 2 trial may include just 50 or up to 300 people.
- Phase 3: At this point, the drug or device is thought to be safe enough to give to large groups of people. Doctors continue to look for side effects, but Phase 3 trials focus more on how well the treatment works. Sometimes a new treatment will be compared to other drugs. A few hundred to a few thousand people may be using the drug or device at this point.
- Phase 4: The treatment is now open to the public, and even larger groups of people are able to use it. The government and drug companies continue to gather data about how the drug works in a larger, more diverse population. They also look for new or different side effects that may come up with long-term use.
Is medical research safe?
All medical research on humans must be approved and monitored by a group of scientists and doctors called an institutional review board (IRB). IRBs must follow rules for human safety set out by the FDA.
If a new treatment appears to be unsafe at any stage, the clinical trial is stopped. The researchers involved then explain what they think went wrong. Often, any medical care related to the trial is provided at no cost because it is experimental.
IRBs and FDA regulations exist to make medical studies as safe as possible for people to join. However, all research has risks. Some risks are predictable and some are not. That is why something called informed consent is so important.
What is informed consent?
Informed consent is the process of making sure a person joining a study understands the potential risks and benefits of that clinical trial. Informed consent includes making sure the person understands what they will need to do to join the study and that they can quit at any time. An informed consent form outlines all of this information.
Who pays for research?
There are a few main sources of funding for health research. The federal government, nonprofits, universities, and pharmaceutical companies all fund research.
Where do studies take place?
Clinical trials take place in hospitals, doctors’ offices, universities, and clinics. Often, a clinical trial will include people from many cities, states, and countries. For the most part, clinical trials are located in major cities.
How to get involved
Joining a clinical trial lets you contribute to your community by sharing your unique health and responses to drugs. To find a study right for you, talk to your doctor, or visit the government’s clinical trial registry at ClinicalTrials.gov.
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