2024 Jan 10. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan–.
ABSTRACT
An adverse drug reaction (ADR) refers to an untoward reaction to a medication. ADRs are common and constitute a significant healthcare burden. The most robust database of ADRs available is the U.S. Food and Drug Administration's Adverse Event Reporting System (FAERS). In 2022, there were over 1.25 million serious adverse events reported and nearly 175,000 deaths. There are 6 emergency department (ED) visits for therapeutic and nontherapeutic medication harms per 1,000 patients, and about 38% of such visits subsequently require hospitalization. Additionally, in 3 out of every 1000 hospital admissions, a patient dies due to an ADR. Thus, ADRs increase morbidity, mortality, hospitalizations, and healthcare costs. Therefore, healthcare professionals must be ready to identify and treat ADRs and prioritize efforts to prevent their occurrence.
ADR Definitions
The International Conference on Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use, of which the World Health Organization (WHO) and the United States Food and Drug Administration (FDA) are members, defines an ADR as "A response to a drug which is noxious and unintended, and which occurs at doses normally used for prophylaxis, diagnosis, or therapy of disease or the modification of physiologic function." An adverse drug event, on the other hand, is defined as: "Any untoward medical occurrence that may present during treatment with a pharmaceutical product, but which does not necessarily have a causal relationship with this treatment." Therefore, an ADR is an adverse event with a causal connection to a drug.
Edwards et al suggested that the above definition is not all-inclusive and defines an ADR as "an appreciably harmful or unpleasant reaction, resulting from an intervention related to the use of a medicinal product, which predicts hazard from future administration and warrants prevention or specific treatment, or alteration of the dosage regimen, or withdrawal of the product." Multiple organizations have offered other definitions for ADRs, though the above will be used for the purposes of this evidence-based resource.