trials overview

Clinical trials are studies in which new drugs are tested for their effectiveness in treating people with diseases such as peripheral neuropathy. When a pharmaceutical company develops a new drug, it sponsors a clinical trial to test the drug in people with the disease for which it was intended. The process is regulated by the Food and Drug Administration (FDA)—  FDA’s approval is required before a drug is allowed to be used. Natural products such as vitamins or food supplements, which are commonly sold in health food stores as alternative medicines, are not regulated by the FDA, and are not required to undergo clinical trials.

What are the phases of clinical trials?

A drug goes through several phases of testing, each phase having a different purpose to help scientists answer different questions:

In Phase I trials, researchers test an experimental drug or treatment in a small group of people (usually 20-100 for the first time) to evaluate the experimental drug’s safety, determine a safe dosage range, and identify side effects. The duration of a phase I trial is relatively short.

In Phase II trials, the experimental study drug or treatment is given to a larger group of people—up to several hundred—to see if it is effective and to further evaluate its safety. Phase two can last several months and longer.

Participants in clinical trials are usually divided into two groups: an investigational group (which receives the new drug) and a control group (which receives either a placebo—a substance that looks like the drug but which has no effect—or an existing drug). To avoid bias, the trials are usually “blinded;” that is, the participants or their physicians do not know whether a person is receiving the investigational drug or the control substance. At the end of the clinical trial, the groups are compared to see whether the drug has a beneficial effect.

In Phase III trials, the experimental study drug or treatment is given to large groups of subjects—1,000-3,000—over a period of up to several years to confirm its effectiveness, monitor side effects, compare it to commonly used treatments, and collect information that will allow the experimental drug or treatment to be used safely.

In Phase IV trials, post-marketing studies explain additional information including the drug's risks, benefits, and optimal use.

Once the FDA approves the drug, it becomes available by prescription. Occasionally, a drug is found to have a beneficial effect in a disease other than the one for which it was tested; when prescribed for that reason, it is called an “off label use.” For example, amytriptyline is approved by the FDA for use in depression, but is widely used for treating the pain of neuropathy. This can create problems with insurance companies who may refuse to pay for a non-FDA approved use of a drug.

Why participate in a Clinical Trial?

The decision to participate in a clinical trial is a personal one.  It should be discussed n with your physician, family and friends.  Most importantly, it should be an informed decision. Participating in a clinical trial allows you to be proactive in the management of your health, have access to new research treatments before they become available to the general public, and help others by contributing to medical research. If you are considering participating in a clinical trial, make it a point to find out as much as you can about the new drug, and discuss the trial with your doctor.

Clinical trials may provide some patients with an option when approved therapies fail. Some other patients may participate in trials because they want to contribute to the advancement of medicine. For each clinical trial, researchers develop eligibility criteria, such as age, sex, type and stage of disease, previous treatment history, and other medical conditions. Criteria like these help to diminish the amount of variation in the study—without threatening the scientific integrity of the trial—by removing medical variations that might complicate the analysis of the results.

Not everyone who applies for a clinical trial will be accepted. Volunteers may be excluded based on the eligibility criteria and/or the number of participants needed by the researchers to collect enough information to determine the safety and effectiveness of a therapeutic agent.

This is an interactive online database managed by the National Library of Medicine.  It allows a visitor to be notified about recruitment for future studies. To learn more about clinical trials and find updated information about federally and privately supported clinical research in human volunteers, please visit
This site provides a wealth of information for patients looking to participate in clinical trials and for research professionals. It includes a listing of more than 41,000 active industry and government-sponsored clinical trials, as well as new drug therapies in research and those recently approved by the FDA.
To receive alerts via e-mail of studies that match your interests, complete the online questionnaire that WebMd provides. Alternatively you can perform a search for specific studies.



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