[Chiral switch, a successful way for developing drugs: example of esomeprazole]

About 25% of common drugs are racemates, i.e. mixtures of their optical or spatial isomers (stereoisomers or enantiomers). Frequently the enantiomers differ in their pharmacokinetics, pharmacodynamics, drug interactions and side effects. Therefore, the pharmaceutical industry, pharmacologists and clinicians are increasingly interested in the development of enantiomers as drugs. Since advances in synthetic and analytical chemistry have provided the tools to produce stereoisomeric drugs, also the authorities recommend and support chiral switch. As example for the therapeutic gain the recent studies with esomeprazole, the first isomeric protonpump inhibitor (iPPI) are summarized and discussed.