Clinical trials - process used to evaluate the effectiveness and safety of medications or medical devices by monitoring their effects on large groups of people. Typically, the Food and Drug Administration approves or disapproves new treatments based on clinical trial results. For some patients, clinical research trials represent an avenue for receiving promising new therapies that would not otherwise be available. Patients with difficult to treat or currently "incurable" diseases, may want to pursue participation in clinical research trials if standard therapies are not effective.

Phase I trial - the earliest stage clinical trial for studying an experimental drug in humans. Phase I trials are generally comparatively small and are used to determine toxicity and maximum dose. They provide an initial evaluation of a drug's safety and how the drug is absorbed, what tissues it reaches, and how long it takes to leave the body. Such studies also usually test various doses of the drug (dose-ranging) to obtain an indication of the appropriate dose to use in later studies. The patients in these trials usually have advanced disease and have already received best available treatment.

Phase II trial - usually focuses on the activity of the new product or drug as a single agent in an open study. Phase II trials look at side effects and how well the drug works. A phase II trial is a noncomparative study, meaning that the therapeutic effects and side effects of the agent are not compared to another drug or a placebo.

Phase III trial - phase III trials are conducted to conclusively show how well a drug works when compared to other drugs. Phase III trials are large, frequently multi-institution, studies. They generally compare the relative value of the new drug with the current standard treatment. They measure whether a new drug extends survival or otherwise improves the health of patients on treatment (clinical improvement). These studies generally are larger and last longer than phase II trials.

Controlled clinical trial - a clinical trial in which the variables are controlled so that the effects of varying one factor at a time may be observed. For example, participants in a controlled trial divided into two or more groups and the drug will be compared to another drug or a placebo. All of the participants will have similar characteristics and will be in similar stages if their disease.

Randomized clinical trial - A study in which the participants are assigned by chance to separate groups that compare different treatments; neither the researchers nor the participants can choose which group. Using chance to assign people to groups means that the groups will be similar and that the treatments they receive can be compared objectively. At the time of the trial, it is not known which treatment is best. It is the patient's choice to be in a randomized trial.

For more information regarding the clinical trial process visit: http://www.nih.gov/health/clintr.htm