EVALUATION IN HUMANS
Less than one third of the drugs tested in clinical trials reach the marketplace. Federal law in the USA and ethical considerations require that the study of new drugs in humans be conducted in accordance with stringent guidelines. Scientifically valid results are not guaranteed simply by conforming to government regulations, however, and the design and execution of a good clinical trial require interdisciplinary personnel including basic scientists, clini-cal pharmacologists, clinician specialists, statisticians, and others. The need for careful design and execution is based on three major confounding factors inherent in the study of any drug in humans.