[Pharmacogenetics I. Concept, history, objectives and areas of study].

There is great interindividual variability in the response to drugs, both in effectiveness and toxicity. Different patients respond differently to the same medication as a consequence of genetic and non-genetic factors. Pharmacogenetics represents the study of the individual pharmacological response based on the genotype. Its objective is to optimize treatment in an individual basis, thereby creating an individualized therapy, more safe and efficient, that will allow the clinician to select the correct drug, at the adequate dose, for the right patient. In the first part of this review we discuss several aspects of the relationship between genetics and therapeutic response, as well as the concept, history, objectives and different areas of study of pharmacogenetics.