Pharmacoepidemiology

Definition, scope & rationale

• Definition — Pharmacoepidemiology = the application of epidemiologic methods and reasoning to the study of the use of, and the beneficial and adverse effects of, drugs in large human populations — population-level study of drug exposures and outcomes using observational designs and routinely-collected real-world data.
• Why it exists — Rare but serious ADRs are usually identified only after a drug is in widespread clinical use — the thalidomide–phocomelia catastrophe (>10,000 affected children, 1957–61) is the founding example that drove national post-marketing surveillance worldwide.
• Engine of post-marketing safety — Signals raised by spontaneous reports are refined and quantified by observational pharmacoepidemiologic studies before regulatory action; it supplies the quantitative arm of the life-cycle view of drug safety.
• Life-cycle principles — Safety/efficacy are not fixed at approval; risk is driven not only by rare ADRs but by an increased risk of common events (e.g. MI with rofecoxib); risk-mitigation can keep useful but hazardous drugs on the market (e.g. thalidomide for myeloma).
• Relation to pharmacovigilance — Pharmacovigilance (WHO 2002) = "the science and activities relating to the detection, assessment, understanding and prevention of adverse effects or any other drug-related problems." Pharmacoepidemiology supplies the population-based methods (cohort/case-control, prescription-event monitoring, record-linkage, signal detection) that move pharmacovigilance from anecdotal signal to measured association.