Pharmacoepidemiology

Bridging Pharmacology and Epidemiology

Clinical pharmacology, which is the study of how drugs interact with humans to produce beneficial or deleterious effects, seeks to provide a risk benefit assessment for individual patients. Epidemiology, which is the main science behind the field of public health, is the study of the distribution of disease and the factors affecting the health and illness of populations. Applying epidemiological methods to clinical pharmacology allows one to provide an estimate of the probability of beneficial effects in populations, or conversely, the probability of adverse effects in populations.

Pharmacoepidemiology benefits from the methods developed in general epidemiology, which has its origins in the study of infectious diseases in large populations. Researchers usually perform pharmacoepidemiological studies on drugs once they are marketed.

Pharmacoepidemiology is a rigorous science, but has limitations. For example, although one can use pharmacoepidemiological methods to determine whether an association between a drug exposure and an outcome exists, one cannot ascertain a causal relationship, nor can one use this science to explain the nature or mechanism of adverse drug reactions or beneficial effects.

Importance and Application

Pre-marketing clinical studies usually test an investigational new drug in several hundred to several thousand people. Once a drug is approved and marketed, tens of thousands to millions of people may be exposed to the medication. Even though one of the primary objectives of the drug development and approval process is to ensure that drugs are safe before marketing commences, conventional randomized clinical trials are often inadequate to detect and assess rare adverse events associated with exposure to the drug.

For example, if a drug causes kidney failure in one out of 1,000 patients, clinical trials conducted in relatively few patients may not detect this serious adverse effect. If 100,000 patients consume the drug annually once it is marketed, kidney failure will occur in a considerable number of patients and this information is essential to protecting the public's health.

Post-marketing drug surveillance, which is often used interchangeably with pharmacovigilance, is the most common application of pharmacoepidemiology. Pharmacovigilance is a process of continual monitoring for adverse effects of drugs that are already on the [Page 1367]market and refers almost exclusively to spontaneous reporting systems, which allow regulators and health-care providers to report adverse drug reaction 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 otherwise. One example is the MedWatch system maintained by the FDA in the U.S.

Training and Practice

The study of pharmacoepidemiology typically involves substantial didactic work in general epidemiology, biostatistics, and health services research, and usually succeeds more clinically oriented training in medicine, pharmacy, pharmacology, or related disciplines. Pharmacoepidemiologists usually work as researchers in regulatory agencies, in the pharmaceutical industry, in contract research organizations, or in consulting firms; or as researchers and professors in academia.

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