Clinical trials are research studies performed in people that are aimed at evaluating a medical, surgical, or behavioral intervention. They are the primary way that researchers find out if a new treatment, like a new drug or diet or medical device (for example, a pacemaker) is safe and effective in people. Often a clinical trial is used to learn if a new treatment is more effective and/or has less harmful side effects than the standard treatment.
Other clinical trials test ways to find a disease early, sometimes before there are symptoms. Still others test ways to prevent a health problem. A clinical trial may also look at how to make life better for people living with a life-threatening disease or a chronic health problem. Clinical trials sometimes study the role of caregivers or support groups.
Before the U.S. Food and Drug Administration (FDA) approves a clinical trial to begin, scientists perform laboratory tests and studies in animals to test a potential therapy’s safety and efficacy. If these studies show favorable results, the FDA gives approval for the intervention to be tested in humans.
Clinical trials advance through four phases to test a treatment, find the appropriate dosage, and look for side effects. If, after the first three phases, researchers find a drug or other intervention to be safe and effective, the FDA approves it for clinical use and continues to monitor its effects.
Clinical trials of drugs are usually described based on their phase. The FDA typically requires Phase I, II, and III trials to be conducted to determine if the drug can be approved for use.
A Phase I trial tests an experimental treatment on a small group of often healthy people (20 to 80) to judge its safety and side effects and to find the correct drug dosage.
A Phase II trial uses more people (100 to 300). While the emphasis in Phase I is on safety, the emphasis in Phase II is on effectiveness. This phase aims to obtain preliminary data on whether the drug works in people who have a certain disease or condition. These trials also continue to study safety, including short-term side effects. This phase can last several years.
A Phase III trial gathers more information about safety and effectiveness, studying different populations and different dosages, using the drug in combination with other drugs. The number of subjects usually ranges from several hundred to about 3,000 people. If the FDA agrees that the trial results are positive, it will approve the experimental drug or device.
A Phase IV trial for drugs or devices takes place after the FDA approves their use. A device or drug's effectiveness and safety are monitored in large, diverse populations. Sometimes, the side effects of a drug may not become clear until more people have taken it over a longer period of time.
There are many reasons why people choose to join a clinical trial. Some join a trial because the treatments they have tried for their health problem did not work. Others participate because there is no treatment for their health problem. By being part of a clinical trial, participants may find out about new treatments before they are widely available. Some studies are designed for, or include, people who are healthy but want to help find ways to prevent a disease, such as one that may be common in their family.
Many people say participating in a clinical trial is a way to play a more active role in their own health care. Other people say they want to help researchers learn more about certain health problems. Whatever the motivation, when you choose to participate in a clinical trial, you become a partner in scientific discovery. And, your contribution can help future generations lead healthier lives. Major medical breakthroughs could not happen without the generosity of clinical trial participants—young and old.
Here’s what happens in a trial:
Study staff explain the trial in detail and gather more information about you.
Once you have had all your questions answered and agree to participate, you sign an informed consent form.
You are screened to make sure you qualify for the trial.
If accepted into the trial, you schedule a first visit (called the “baseline” visit). The researchers conduct cognitive and/or physical tests during this visit.
You are randomly assigned to a treatment or control group.
You and your family members follow the trial procedures and report any issues or concerns to researchers.
You may visit the research site at regularly scheduled times for new cognitive, physical, or other evaluations and discussions with staff. At these visits, the research team collects information about effects of the intervention and your safety and well-being.
You continue to see your regular physician for usual health care throughout the study.
After you consent, you will be screened by clinical staff to see if you meet the criteria to participate in the trial or if anything would exclude you. The screening may involve cognitive and physical tests.
Inclusion criteria for a trial might include age, stage of disease, sex, genetic profile, family history, and whether or not you have a study partner who can accompany you to future visits. Exclusion criteria might include factors such as specific health conditions or medications that could interfere with the treatment being tested.
Many volunteers must be screened to find enough people for a study. Generally, you can participate in only one trial or study at a time. Different trials have different criteria, so being excluded from one trial does not necessarily mean exclusion from another.