[From concept to active substance: genesis of a new drug]

The systematic development of drugs is not new. This is shown by Withering's endeavour, 200 years ago, to make a useful therapeutic agent out of the digitalis plant. Today the way from idea to drug is long, taking about 10 to 15 years, and very expensive. A selection of approaches to drug discovery is described and illustrated with a practical example, the development of isradipine. In this example emphasis is placed on tissue selectivity, which even today remains an interesting research problem. One of the theories, suited to explain tissue selectivity, is also exposed.