What is defined as an adverse drug reaction?

An adverse drug reaction is characterized as an unintended harmful response that occurs following the administration of a medication. This distinction is crucial as it emphasizes that the response is negative and not anticipated by the prescribing healthcare provider. Adverse drug reactions can vary in severity and may manifest in various ways, including allergic reactions, system toxicity, or unexpected changes in a patient’s health status that arise as a direct consequence of the medication.

The definition excludes beneficial effects or therapeutic outcomes, as those are considered intended and positive responses to a drug. It also differentiates from common side effects, which although they might be expected, are not defined as adverse reactions unless they lead to harm. Furthermore, an expected change in patient condition does not qualify as an adverse drug reaction, as these changes are anticipated based on clinical knowledge about the drug's effects. Thus, the correct definition aligns specifically with the concept of an unintended and harmful response, guiding healthcare providers in monitoring and managing any risks associated with medication therapy.