Pharmacoepidemiology

Pharmacoepidemiology is the study of the use and effects of drugs in large groups of people.

To accomplish this study, pharmacoepidemiology borrows from both pharmacology and epidemiology. Thus, pharmacoepidemiology can be called a bridge science spanning both pharmacology and epidemiology. Pharmacology is the study of the effect of drugs and clinical pharmacology is the study of effect of drugs in humans. Part of the task of clinical pharmacology is to provide a risk benefit assessment for the effect of drugs in patients. Doing the studies needed to provide an estimate of the probability of beneficial effects in populations, or the probability of adverse effects in populations and other parameters relating to drug use may benefit from using epidemiological methodology. Pharmacoepidemiology then can also be defined as the application of epidemiological methods to pharmacological issues.

Epidemiology can be defined as the study of the distribution and determinants of diseases in populations. Epidemiological studies can be divided into two main types:
 * 1) Descriptive epidemiology describes disease and/or exposure and may consist of calculating rates, e.g., incidence and prevalence. Such descriptive studies do not use control groups and can only generate hypotheses, not test them. Studies of drug use would generally fall under descriptive studies.
 * 2) Analytic epidemiology includes two types of studies: observational studies, such as case-control and cohort studies, and experimental studies which would include clinical trials such as randomised clinical trials. The analytic studies compare an exposed group with a control group and are usually designed as hypothesis testing studies.

Pharmacoepidemiology benefits from the methodology developed in general epidemiology and may further develop them for applications of such methodology unique to pharmacoepidemiology. There are also some areas that are altogether unique to pharmacoepidemiology, e.g., pharmacovigilance. Pharmacovigilance is a type of continual monitoring for unwanted effects and other safety-related aspects of drugs that are already on the market. In practice, pharmacovigilance refers almost exclusively to the spontaneous reporting systems which allow health care professionals and others to report adverse drug reactions to a central agency. The central agency can then combine reports from many sources to produce a more informative safety profile for the drug product than could be done based on one or a few reports from one or a few health care professionals.