The design of clinical trials in psoriasis: lessons for clinical practice.

Understanding the process by which drugs are approved gives clinicians a better understanding of the medications they prescribe and how these medications are best used to care for patients. The development of new drugs in the United States proceeds through a series of studies culminating in well-designed, large-scale human trials. These studies result from a coordinated collaboration between industry and the Food and Drug Administration (FDA). The results of these studies determine whether drugs are approved for use or not. They also determine the labeling and marketing of products and guide (but do not fully determine) physicians' use of the drug. This article follows a hypothetical drug for use in psoriasis through the approval process, in order to illustrate the process and its implications for clinical practice.