Pharmacoepidemiology is that the study of interactions between drugs and human populations, investigating, in real conditions of life, benefits, risks and use of medicine . Pharmacoepidemiology applies to drugs the methods and/or reasoning of both pharmacology and epidemiology. the event of pharmacoepidemiology should improve the "rational drug use". Pharmacoepidemiology is an emerging field to know the utilization of medicines during a large population, identify and quantify adverse drug reactions during a population, and to quantify the danger or advantage of taking a medicine for a specific disease or condition. Increasingly, secondary data are getting more available with computerization of medical records and billing procedures. Pharmacoepidemiology has established and robust study designs that provide strong evidence for the drugs within the relationship to outcomes. Pharmacoepidemiology results are often utilized in conjunction with other data to elucidate or identify areas of need and improve the health outcomes.