[The effect of cancer on drug metabolism and drug action].

Over the last few years, numerous studies performed mainly in animals with a tumour but also in man with malignant disease have shown that the presence of cancer modifies gastro-intestinal absorption, tissue distribution and transformation of drugs in the liver. Consequently, malignant disease also influences the therapeutic effects and toxic effects of drugs. This effect may occur with several drugs, with or without antineoplastic properties, and appears mainly at an advanced stage of the disease.