Pharmacogenetics; mini review

If it were not for the great variability among individuals medicine might as well be a science and not an art.” The thoughts of Sir William Osler in 1892 reflect the view of medicine over the past 100 years.1 Modern pharmacogenetics has its origins in the 1950s with a series of discoveries.2 The genetic basis underlying variations in drug response has become evident with the introduction of modern analytical methods for analysis of gene sequence and expression. Pharmacogenetics is the study of how the genes affect the way people responds to therapy. There is great heterogeneity in the way people respond to the medications in term of toxicity and treatment efficiency.3 The variations in response may be due to environmental factors or genetic factors. The environmental factor which influences the response can be other drugs, nutritional components, smoking or liver disease; they can cause the difference in activity either by inducing or inhibiting the drug metabolizing enzymes. In last few years, it has been realized that common genetic polymorphism of metabolizing enzymes can affect the response of individuals towards drugs. Genetic polymorphisms of drug metabolizing enzymes give rise to distinct subgroups in the population which differs in their ability to perform a certain drug biotransformation reactions. The goal of Pharmacogenetics is to individualize drug therapy to a person’s unique genetic makeup.4 Genetic makeup determines the inherent pharmacokinetics, which shows the interpersonal differences in drug absorption, distribution, metabolism and elimination. These differences can be explained by genetic variation in transport proteins, drug targeting, and in function of cytochrome P450 or phase 2 drug metabolizing enzymes.