News & Research

What are the different phases of clinical trials?

Clinical trials are traditionally divided into different phases. Each phase is designed to gather specific information about the drug or treatment being studied.

Phase I trials

These trials are the first human tests of new drugs or therapies. They typically involve small numbers of volunteers and are designed to determine the best dose of the drug and to check for any side effects. Because Phase I trials use treatments that have never been tested in humans, they may involve significant risks.

Phase II trials

If a treatment is shown to be safe and well tolerated, it moves on to Phase II trials. These trials involve many more volunteers and are designed to see how well the treatment works, usually in a small group of patients.

Phase III trials

If the treatment is effective in Phase II trials, it moves on to Phase III trials. Hundreds or even many thousands of patients may participate in these studies. They are aimed at further testing how well the treatment works. Often Phase III trials compare the new treatment to an already existing, standard treatment in a randomized fashion.

Phase IV trials

These trials are conducted after a drug has been approved by the FDA and is on the market. Phase IV trials typically involve a very large number of participants and are designed to evaluate new uses of existing therapies or to detect side effects that were not apparent during Phase III studies.

How are clinical trials conducted?

The doctors and researchers running a clinical trial develop a written plan detailing exactly how the trial will be conducted. This plan, also called a protocol, explains how the trial will be run, what information will be gathered, and what new things the researchers hope to learn.

Many clinical trials compare a new treatment to a standard treatment. In these trials, participants are divided into two groups. One group receives the new treatment and one group (the "control" group) receives the standard treatment. Various statistics are then gathered using blood, x-ray, and other tests to assess how well each group responds to the two kinds of treatment.

In order to prevent biased results or interpretation, many trials assign participants by chance to one of these two groups. This process, known as randomization, is only used when it is not known which treatment option will work better.

Related links

About IRBs

Who pays for the treatment in a clinical trial?

For the most part, the drugs used in clinical trials are given free of charge to the study participants. However, there may be other costs associated with the trial, such as blood work, x-ray tests, and travel expenses. Health insurance may cover some of these items and some may be offered free of charge. Medicare now covers all routine patient care costs associated with clinical trials. The financial details should be discussed prior to enrolling in a trial.

Related links

Clinical Trials and Insurance Coverage

Medicare Coverage of Clinical Trials

Coverage Issues Manual

The content on this page was written by Dr. Marc Engelsgjerd and Michael D'Agostino of Veritas Medicine