What is an adverse drug reaction (ADR)?

An adverse drug reaction (ADR) is defined as an unintended and harmful response to a medication. This type of reaction can occur after the administration of a drug, even when the medication is used as intended and in the correct dosage. ADRs can range from mild effects, like nausea or rash, to severe complications, such as organ damage or even death. Recognizing ADRs is crucial in pharmacology because they impact patient safety and treatment outcomes, highlighting the importance of monitoring and reporting these events in clinical practice.

In contrast, the other options describe expected outcomes or intended positive effects associated with medication use, which are not classified as adverse reactions. Thus, they do not accurately represent the concept of an ADR. Understanding this distinction is vital for anyone studying pharmacology, as it informs clinical decision-making and enhances patient care.