[Clinical trials. An overview].

Since the mid-1950s, the basis for evaluating medical therapies has shifted from transferred knowledge, subjective impression and personal experience towards clinical trials, first, in reaction to side effect tragedies, in drug licensing, then to a growing extent in other parts of medicine such as the assessment of medical devices or surgical procedures. Clinical trials are prospective studies of the efficacy and safety of therapies by repeated application. For this purpose, therapies are usually compared to controls, based on statistical reasoning. Initial comparability of study groups is best guaranteed by randomisation while equality of observation and of concomitant treatment is best guaranteed by blinding. Clinical trials do not result in clear-cut yes/no answers, but reduce the range of reasonable interpretations regarding efficacy and safety of a therapy. Thus, they allow decisions to be made on solid objective grounds. In this way, clinical trials have contributed substantially to medical progress over the last 50 years and are indispensable for today's medical research.