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On an almost daily basis, people read or hear about new drug discoveries and adverse reactions supposedly caused by drugs on the market. Sometimes panic sets in because a drug seems to be responsible for the death of some of its users, but how can people evaluate what they read and hear? How are adverse reactions and side effects studied and measured? How are a drug’s beneficial effects determined? To answer these questions and many others about medications and drugs used in society, data and information are gathered and analyzed through pharmacoepidemiological study.

In this book, the principles and practice of pharmacoepidemiology are presented and discussed in the contexts of epidemiology and public health. In an attempt to prevent or reduce the occurrence of disease, public health professionals realized a scientific method was needed to assess diseases and their causes. In essence, they needed to develop a logical, standard approach to counting events (e.g. births, deaths, disease) and calculating results from the data. The field of epidemiology was born in the 19th century to address this need. In the latter half of the 20th century, epidemiologists applied the basic principles of their discipline to study the occurrence of drug use and associated problems. Thus, at the foundation of pharmacoepidemiology is epidemiology.

In this chapter, the basic aspects of epidemiology and public health are introduced as the basis for understanding pharmacoepidemiology. The host–agent–environment model is presented as the guide to comprehending disease occurrence and transmission in a population.

Whereas epidemiology is the study of disease occurrence and transmission in a human population, epidemiological studies focus on the distribution and determinants of disease. Epidemiology may also be considered the method of public health—a scientific approach to studying disease and health problems. Epidemiology consists of research methods and specific strategies for counting and calculating the occurrence and risk of disease. Therefore, epidemiological studies of drug use employ these methods and statistical measures to study the occurrence and distribution of drug use and its associated problems. Examples of epidemiology applied to drug use include adverse drug reaction reporting, postmarketing surveillance studies, and clinical drug trials.

One major difference between the clinician’s and the epidemiologist’s perspective is the focus on individual patients versus the population at large. For example, health professionals are educated to focus on individual patient problems, and pharmacists are trained to consider individual patient variability in response to drug therapy. The focus in both of these areas in health care emphasizes interactions with individual patients. Health professionals sometimes assume that if their patient has a problem with a drug, then many other patients also have the same problem. This assumption may be flawed because the nature and extent of the problem in other patients cannot be known by these health professionals. Only by studying large groups of people (ie, populations) can the magnitude and reasons for a problem be determined.

In contrast, the public ...

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