Clinical Trials

What are Clinical Trials?

A clinical trial is a human research study designed by scientists and medical experts to answer questions about a disease and potential new therapies. They are an essential component of the scientific research process. Simply put, there is no other way for research to show that a potential treatment works.

Learn more by reading below:

Do all clinical trials test drug therapies?

There are two main types of clinical trials: interventional and observational.

Interventional trials determine whether experimental treatments or new ways of using known therapies are safe and effective. These trials might ask a participant to take an experimental new drug or undergo surgery.

Observational trials address health issues in large groups of people or populations in natural settings. Participants in these trials may be asked to answer questions about their family histories or give blood samples, but they do not receive treatment for their disease. Some observational trials are even open to healthy volunteers.

How are clinical trials conducted?

Clinical trials that test drugs are conducted in a series of carefully monitored phases designed to answer specific questions.

Phase I: In a Phase I trial, researchers test a new drug or treatment in people for the first time. A small group of people, typically fewer than 100, are monitored to evaluate the drug or treatment's safety, determine a safe dosage range, and identify side effects.

Phase II: Phase II trials study the effectiveness of a drug or treatment in a larger group of people.

Phase III: In this phase, the study drug or treatment is given to a large group of several hundred to several thousand people. This large-scale testing gives more detailed information about the drug's benefits, effectiveness, and the range of possible side effects.

Phase IV: Phase IV studies are usually conducted on drugs that have already been approved by the FDA. These trials are run to determine additional uses for an approved drug or further study its safety in large numbers of participants.

Benefits and Risks of Clinical Trials

Participating in a clinical trial can be a rewarding experience. Consider the following benefits when deciding if you should join a clinical trial:

  • You will have access to leading healthcare professionals, cutting-edge new treatments and high standards of care.
  • Joining a clinical trial can increase your knowledge and understanding of your disease.
  • People who take part in clinical trials are contributing to science that may benefit themselves and others. The medications that you take now are available only because people before you have volunteered in clinical trials.

Although every effort is made to ensure that clinical trials are as safe as possible, clinical trials that test new therapies are experiments and can involve risks.

Here are some of the risks to consider:

  • There may be undesirable side effects to the treatment. A health professional will explain possible risks and side effects during the informed consent process.
  • The treatment may not be effective for the participant.

People with PD should also keep in mind that they may not receive the experimental treatment because they may be randomly assigned to the "control" group and receive either a different dose of the "test" treatment, a treatment that is already available that is considered standard therapy for the disease, or a sugar pill (placebo). The control group is used as a basis for comparison. In many studies, the researcher is not aware of who is taking the treatment and who is in the control group. The study might have time and travel requirements that are demanding. These are some issues you should address when talking to a clinical investigator.

How Can I Learn More About Clinical Trials?

If you are interested in research, you may want to consider applying to become a PDF Research Advocate, so you can be trained to influence research and speed new and effective treatments for Parkinson's.

Browse information about the Parkinson's Advocates in Research program to learn how you can get involved.


Fox Trial Finder
Fox Trial Finder is a web-based clinical trial matching tool to connect those with and without Parkinson's disease to Parkinson's clinical research opportunities that urgently need their participation. After volunteers input information about themselves (such as zip code, date of birth, and brief medical history), Fox Trial Finder provides trial match suggestions. Fox Trial Finder also provides the opportunity for volunteers to connect directly with trial coordinators through a secure messaging interface on the site. Register for Fox Trial Finder today to play a part in accelerating recruitment into PD clinical research.

An information service for patients, pharmaceutical companies and research centers that are involved in clinical research. Centerwatch publishes a wide range of newsletters, books and directories.

  • Review an extensive list of clinical trials being conducted across the world.
  • Subscribe to a free email service which notifies you about new Parkinsons clinical trials in your area.

National Institutes of Health
A resource site developed by the National Institutes of Health to provide patients, family members and the general public with current information about clinical research studies.

  • Find out about current PD clinical trials.
  • Access information describing the clinical trials process.

Parkinson Study Group (PSG)
A nonprofit, cooperative group of Parkinsons disease experts from medical centers in the US and Canada dedicated to improving PD treatments through clinical trials.

  • Identify references in scientific and academic journals relating to PD research and clinical trials.
  • Find out about PSG clinical trials that are in progress.

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More Questions?

Do you have more questions about clinical trials? Ask the experts your questions by email or call our helpline at (800) 457-6676.