What is defined as an "adverse drug reaction" (ADR)?

An "adverse drug reaction" (ADR) is characterized as a harmful or unintended response that occurs at normal therapeutic doses of a medication. The key aspect of this definition is that ADRs can occur even when the drug is used as intended and dosed appropriately. They can manifest in various forms, ranging from mild effects to severe reactions, but they are specifically associated with harm or injury caused by the medication. Recognizing ADRs is critical for healthcare providers since they can significantly impact patient safety, compliance, and the effectiveness of treatment plans.

The other options do not accurately capture the essence of what constitutes an ADR. Positive health responses to medication generally denote the intended therapeutic effects rather than adverse outcomes. Expected reactions due to medication overuse relate more to toxic effects or overdoses rather than standard dosing arguments. Lastly, mild side effects that resolve quickly are typically not classified as ADRs if they do not cause any harm or require medical intervention, as they are understood to be common and not concerning at therapeutic doses.