Pharmacoepidemiologic studies offer assessments of potential short and long-run adverse drug events within the general population with a wide range of health status and demographic characteristics and with a way longer follow-up period than clinical trials that measure initial drug effectiveness and safety. It embody live population primarily based benefits and risks of drug in large numbers of individuals. Studies includes the analysis of prescribing medication and its determinant factors, implementation of pharmaco-epidemiologic information into action, describe and analyze the economics of drug use and to advise decision-makers. Pharmacoepidemiology is the study of the uses and effects of drugs in well defined populations. To accomplish this study, pharmacoepidemiology borrows from both pharmacology and epidemiology. Thus, pharmacoepidemiology is the bridge between both pharmacology and epidemiology. Pharmacoepidemiology is the study of the utilization and effects of drugs in large numbers of people Pharmacoepidemiology applies epidemiological methods to studies of the clinical use of drugs in populations. A modern definition of pharmacoepidemiology is the study of the use and effects/side-effects of drugs in large numbers of people with the purpose of supporting the rational and cost-effective use of drugs in the population thereby improving health outcomes