clinical pharmacology
Adverse Drug Reactions
Introduction
Adverse drug reaction (ADR, or adverse drug effect) is a broad term referring to unwanted, uncomfortable, or dangerous effects that drugs (including medications ) may have. Adverse drug reactions can be considered a form of toxicity; however, toxicity is most commonly applied to effects of General Principles of Poisoning (accidental or intentional) or to elevated blood levels or enhanced drug effects that occur during appropriate use (eg, when drug metabolism is temporarily inhibited by a disorder or another drug). For information on toxicity of specific drugs, including medications, see the table Because all drugs have the potential for adverse drug reactions, conducting a Balancing Drug Benefits and Adverse Effects (the likelihood of benefit vs risk of ADRs) is necessary whenever a medication is prescribed. The National Electronic Injury Surveillance System–Cooperative Adverse Drug Event Surveillance Project (NEISS–CADES) estimated that there were 6 emergency department (ED) visits for medication harms per 1000 persons per year in the period from 2017 to 2019 based on a sample of almost 100,000 cases ( General references ). About 39% of these visits resulted in hospitalization ( Incidence and severity of adverse drug reactions vary by patient characteristics (eg, age, sex, ethnicity, coexisting disorders, genetic or geographic factors) and by drug factors (eg, type of drug, Drug Absorption , treatment duration, dosage, ADRs are more severe among older patients (see Drug-Related Problems in Older Adults ), although age per se may not be the primary cause. Fatal adverse drug reactions occur mainly in patients older than 75 years of age, according to the World Health Organization's pharmacovigilance database ( Adverse drug reactions occur in 10 to 20% of hospitalizations. About 10 to 20% of these reactions are severe. 