a service of the NIH
A clinical trial is a research study to answer specific questions
about vaccines or new therapies or new ways of using known treatments.
Clinical trials (also called medical research and research studies)
are used to determine whether new drugs or treatments are both safe
and effective. Carefully conducted clinical trials are the fastest
and safest way to find treatments that work.
Ideas for clinical trials usually come from researchers. Once researchers
test new therapies or procedures in the laboratory and get promising
results, they begin planning Phase I clinical trials.
New therapies are tested on people only after laboratory
and animal studies show promising results.
All clinical trials are based on a set of rules called a protocol.
It describes what types of people may participate in the trial;
tests, procedures, medications, and dosages; and the
length of the study. Participants are seen
regularly by the research staff to monitor their health and to determine
the safety and effectiveness of their treatment.
Clinical trials of experimental drugs proceed through four phases:
- In Phase I clinical 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.
- In Phase II clinical 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.
- In Phase III studies, 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.
- Phase IV studies are done after the drug or treatment has been
marketed. These studies continue testing the study drug or treatment
to collect information about their effect in various populations
and any side effects associated with long-term use.
The government has strict guidelines and safeguards to protect people
who choose to participate in clinical trials. Every clinical trial
in the U.S. must be approved and monitored by an Institutional Review
Board (IRB) to make sure the risks are as low as possible and are
worth any potential benefits.
Informed consent is the process of learning the key facts about a
clinical trial before you decide whether or not to participate. These
facts include:
- Why the research is being done.
- What the researchers want to accomplish.
- What will be done during the trial and for how long.
- What risks are involved in the trial.
- What benefits can be expected from the trial.
- What other treatments are available.
- The fact that you have the right to leave the trial at any time.
If you are considering joining a clinical trial, the research staff
will give you informed consent documents that include the details
about the study. If English is not your native language, you can ask
for the consent documents in languages other than English. Since joining
a clinical trial is an important decision, you should ask the research
team any questions you may have about the study and the consent forms
before you make a decision.
It is also a good idea to take the consent documents home and discuss
them with family members or friends. Talking about your options can
help you to feel comfortable with your decision. If you decide to
join the clinical trial, be sure to ask for a copy of the informed
consent documents so you can review them at any time.
Remember informed consent is more than signing a form. It is a process
that continues through the study. You should feel free to ask the
research team questions before, during, and after the study. Informed
consent continues as long as you are in the study.
All clinical trials have guidelines about who can get into the program.
Guidelines are based on such factors as age, type of disease, medical
history, and current medical condition. Before you join a clinical
trial, you must qualify for the study. Some research studies seek
volunteers with illnesses or conditions to be studied in the clinical
trial, while others need healthy volunteers. Healthy volunteers participate
in Phase I trials, vaccine studies, and trials on research on preventive
care for children or adults.
The factors that allow you to participate in a clinical trial are
called inclusion criteria and the factors that keep you from
participating are called exclusion criteria. It is important
to note that inclusion and exclusion criteria are not used to reject
people personally. Instead, the criteria are used to identify appropriate
participants and keep them safe. The criteria help ensure that researchers
will be able to answer the questions they plan to study.
Clinical trials are sponsored by government agencies: such as the
National Institutes of Health (NIH); pharmaceutical companies; individual
physician- investigators; health care institutions such as health
maintenance organizations (HMOs); and organizations that develop medical
devices or equipment. Trials can take place in a variety of locations,
such as hospitals, universities, doctors' offices, or community clinics.
The clinical trial process depends on the kind of trial you participate
in. The team will include doctors and nurses as well as social workers
and other health care professionals. They will check your health at
the beginning of the trial, give you specific instructions for participating
in the trial, monitor you carefully during the trial, and stay in
touch with you after the study.
Some clinical trials involve more tests and doctor visits than you
would normally have for your illness or condition. For all types of
trials, you will work with a research team. Your participation will
be most successful if you follow the protocol
carefully and stay in contact with the research staff. Some terms
that will help you understand what happens in a trial are defined
below.
A placebo is an inactive pill, liquid, or powder that has no treatment
value. In clinical trials, experimental treatments are often compared
with placebos to assess the treatment's effectiveness. In some studies,
the participants in the control group will receive a placebo instead
of an active drug or treatment.
A control is the standard by which experimental observations are evaluated.
In many clinical trials, one group of patients will be given an experimental
drug or treatment, while the control group is given either a standard
treatment for the illness or a placebo.
A blinded or masked study is one in which participants do not know
whether they are in the experimental or control group in a research
study. Those in the experimental group get the medications or treatments
being tested, while those in the control group get a standard treatment
or no treatment.
A double-blind or double-masked study is one in which neither the
participants nor the study staff know which participants are receiving
the experimental treatment and which ones are getting either a standard
treatment or a placebo. These studies are performed so neither the
patients' nor the doctors' expectations about the experimental drug
can influence the outcome.
Side effects are any undesired actions or effects of drug or treatment.
Negative or adverse effects may include headache, nausea, hair loss,
skin irritation, or other physical problems. Experimental treatments
must be evaluated for both immediate and long-term side effects.
There are both benefits and risks associated with clinical trials.
By participating in a clinical trial, you can:
- Take an active role in your own health care.
- Gain access to new treatments that are not available to the
public.
- Obtain expert medical care at leading health care facilities
during the trial.
- Help others by contributing to medical research.
Clinical trials have risks:
- There may be side effects or adverse reactions to medications
or treatments.
- The treatment may not be effective for you.
- The protocol may require a lot of your
time for trips to the study site, treatments, hospital stays,
or complex dosage requirements.
You should know as much as possible about the research study. It is
important for you to feel very comfortable asking questions and the
staff should answer them in a way you can understand. A list of sample
questions appears below.
- Plan ahead and write down the questions you want to ask.
- Ask a friend or relative to come with you for support and to
hear the responses to your questions.
- Bring a tape recorder so you can replay the discussion after
you get home.
Some questions you might ask about the research include:
- Why is this research being done?
- What is the purpose of the study?
- Who is sponsoring the study?
- Who has reviewed and approved this study?
- Why does the research team think the treatment, drug, or medical
device will work?
Some questions about your participation in the study include:
- Where is the study site?
- What kinds of therapies, procedures, and/or tests will I have
during the trial?
- Will they hurt? If so, for how long?
- How will the tests in the study compare to tests I would have
outside the study?
- How long will the study last?
- How often will I have to go to the study site?
- Who will provide my medical care after the study ends?
- Will I be able to take my regular medications during the trial?
- What medications, procedures, or treatments must I avoid while
in the study?
- What are my responsibilities during the study?
- Will I have to be in the hospital during the study?
- Will the study researchers work with my doctor while I am in
the study?
- Can anyone find out that I am participating in a study?
- Can I talk to other people in the study?
- Will I be able to find out the results of the trial?
Questions about risks and benefits include:
- How do the possible risks and benefits of the study compare
with approved treatments for me?
- What are the possible immediate and long-term side effects?
Other questions include:
- What other treatment options do I have?
- Will I have to pay anything to participate in the study?
- What are the charges likely to be?
- Is my insurance likely to cover those expenses?
Yes. Most clinical trials provide short-term treatments related to
a designated illness or condition, but not extended or complete primary
health care. In addition, by having your health care provider work
with the research team, you can ensure that your other medications
or treatments will not conflict with the clinical
trial protocol.
Yes. You can leave a clinical trial at any time. If you plan to stop
participating, let the research team know why you are leaving the
study.
Some clinical trials will pay you for joining the trial, while others
will not. In some programs, researchers will reimburse you for expenses
associated with participating in the research. Such expenses may include
transportation costs, child care, meals, and accommodations.
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