Pharmacogenetics and personalised medicine

The traditional concern of pharmacogenetics was Mendelian (monogenic) variation, which visibly affected some drug responses. Pharmacogenetics was broadened by the observation that multifactorial genetic influences, in conjunction with environmental factors, usually determine drug responses. Variability of gene expression, a new theme of the science of genetics, also affects pharmacogenetics; for example, enhanced enzyme activity does not necessarily indicate a mutation, but may be the consequence of a drug-induced enhancement of gene expression. Methodological advances permit the conversion of pharmacogenetics into the broad practice of pharmacogenomics; this improves the possibility of identifying genetic causes of common diseases, which means establishing new drug targets, thereby stimulating the search for new drugs. While the main medical effect of pharmacogenetics was an improvement of drug safety, pharmacogenomics is hoped to improve drug efficacy. On the way to personalized medicine, we may stepwise improve the chances of choosing the right drug for a patient by categorizing patients into genetically definable classes that have similar drug effects (as, for example, human races, or any population group carrying a particular set of genes). It is wise to expect that, even after we have reached the goal to establish personalized medicine, we will not have eliminated all uncertainties.