What is an adverse drug reaction (ADR)?

An adverse drug reaction (ADR) refers specifically to an undesirable or harmful reaction that occurs as a result of medication use. ADRs can manifest in various forms, including side effects, allergic reactions, and other unexpected clinical effects. They can occur even at therapeutic doses and are not necessarily indicative of negligence or error in prescribing; rather, they stem from the inherent pharmacological properties of the drug or individual patient factors.

In contrast, expected reactions to medication use indicate predictable responses based on the drug's known benefits or pharmacodynamics, which does not align with the definition of an ADR. A beneficial effect of a medication signifies the desired outcomes of treatment rather than any adverse effects. Furthermore, while some ADRs can be severe or life-threatening, not all life-threatening reactions qualify as adverse drug reactions. Thus, the correct understanding of ADR is integral to a safe and effective approach to pharmacotherapy.