[Drug interactions as a cause of drug side effects]

Adverse drug interactions are a frequent clinical problem. Mechanistically, they can be classified as pharmaceutic, pharmacokinetic and pharmacodynamic interactions. Mostly, however, several different mechanisms are involved in the pathogenesis of adverse drug interactions, which makes their predictability as well as their prevention strongly dependent on the early and adequate recognition of high-risk patients. Such high-risk situations include drug-related (e.g. galenic form, stability, enantiomers), patient-related (e.g. pharmacokinetics, age, genetic disposition) and various exogenous (e.g. polypragmasy, alcohol abuse, food) factors. Especially the recent progress in the molecular characterization of hepatic biotransformation reactions has markedly increased our understanding of many potentially toxic drug interactions. In addition, several alternative compounds with distinct potentials for interactions with other drugs are now available in various therapeutic drug classes. In the future it will be important to further increase our pathophysiologic and pharmacogenetic knowledge, in order to further improve the predictability, prevention, early recognition and therapy of adverse drug interactions.