Which of the following best defines the term 'adverse drug reaction'?

The term 'adverse drug reaction' refers specifically to an unexpected and harmful response to a medication following its administration. This demonstrates the concept that not all drug reactions are beneficial or intended. Adverse drug reactions can occur even at normal doses and may be serious, requiring immediate medical attention. Understanding this definition is crucial for health care professionals in order to monitor patients effectively and manage any potential risks associated with medication therapy.

In contrast, reactions that develop over time typically do not fall under the definition of an adverse reaction, as adverse drug reactions are often acute in nature and arise suddenly. Expected and non-harmful effects of a drug are classified as side effects, which are known outcomes and anticipated responses to the medication's therapeutic use. Lastly, categorizing a drug reaction as a minor side effect would also not align with the definition of an adverse drug reaction, as the term signifies a potentially severe or harmful effect rather than a trivial one.