[Drug-drug interactions you should know!]

Drug-drug interactions (DDI) represent a significant problem in modern medicine. The number of patients with multi-morbidity, who take multiple drugs, is constantly increasing (polypharmacy). The related exponential increase in potential DDI is almost incomprehensible. In this article, we review pharmacodynamic DDI and provide clinically relevant examples. In addition, we extensively review pharmakokinetic DDI (e. g. through the cytochrome P450-system or p-glycoproteins) that can modify the plasma concentration of many compounds, thereby also increasing the likelihood of unwanted side effects. Finally we provide tools, which may help clinicians in their daily practice to identify and avoid potential DDI. In the context of an ageing society receiving polypharmacy, a better awareness of DDI and of strategies to prevent them is expected to reduce mortality and morbidity. © Georg Thieme Verlag KG Stuttgart · New York.