What is the definition of an adverse drug reaction?

An adverse drug reaction is defined as an unintended, harmful response to a medication that occurs at normal doses typically prescribed for therapeutic use. This definition emphasizes that the reaction is both adverse (or harmful) and not related to an expected pharmacological effect of the drug when taken as prescribed. Adverse drug reactions can present in various forms, including allergic reactions, side effects, and toxicities, potentially leading to significant patient harm or complications.

The focus on normal dosing is crucial because an adverse drug reaction can occur even when a medication is used correctly according to established guidelines, which distinguishes it from expected effects at high doses or those that may arise from inappropriate usage. Understanding this concept is essential for pharmacy technicians, as it enables them to monitor patient reactions and engage in effective medication management.