[Drugs in chronic venous insufficiency--the challenge of demonstrating clinical efficacy].

Approximately 90% of German adults show alterations of their lower limb veins; about every fifth suffers from symptoms of chronic venous insufficiency (CVI). With compression therapy showing low compliance, CVI oedemas and accompanying subjective symptoms are frequently treated with anti-oedematous drugs of herbal origin. A guideline outlines the requirements for clinical studies with CVI drugs. Water displacement plethysmometry (volumetry) is the gold standard for determining the reduction ofoedemas. Besides reducing oedemas, drugs should also demonstrate effects on accompanying symptoms influencing quality of life. Despite assistance provided by the guideline, clinical studies in CVI are complex and subject to multiple error sources in planning and execution. The corroboration of successful studies in further confirmatory studies is good practice and demanded by regulatory authorities. This practice reduces the risk of drugs being accepted as effective just based on the play of chance. As an example, placebo controlled studies with an extract from red vine leaves show that a careful definition of patients as well as meticulous study planning and execution can reproducibly verify significant and clinically relevant treatment effects. When evaluating clinical studies it is recommended to refer to the CONSORT statement. Publications missing certain minimum information make interpretation difficult and may result in a biased judgment of the effects of therapy.