What is an adverse drug reaction (ADR)?

An adverse drug reaction (ADR) is defined as an unwanted or harmful reaction that occurs after the administration of a medication. This definition encompasses any negative effects that occur as a response to a drug that may be unexpected or more severe than anticipated.

ADRs can vary in severity and may manifest as mild side effects or as serious health complications that require medical intervention. Understanding this concept is essential in pharmacology, as it highlights the importance of monitoring patients for any adverse effects and managing their medication regimens effectively to ensure patient safety.

In contrast, a positive response to a drug and beneficial effects that exceed expected outcomes focus on the therapeutic and favorable reactions to medications, which do not align with the definition of an ADR. Moreover, while side effects are part of the spectrum of ADRs, not every side effect qualifies as an adverse reaction, particularly if it is mild and expected. Hence, option C accurately captures the essence of what an adverse drug reaction entails.