Which statement best defines an adverse drug reaction?

Which statement best defines an adverse drug reaction?

• A. A side effect is a predictable, often mild effect at standard doses.
• B. A side effect is always harmful.
• C. An adverse drug reaction is a harmful, unintended effect.
• D. An adverse drug reaction is always dose-dependent.

Answer: (C)

An adverse drug reaction is a harmful, unintended effect that occurs when a drug is used at normal therapeutic doses. This captures the key idea: the reaction is not what was intended, and it causes harm, even though the drug is being taken as prescribed. The other statements mix in elements of side effects or misstate how ADRs occur. Side effects can be predictable and mild, but that doesn’t define an adverse drug reaction. It’s not correct to say a side effect is always harmful. And ADRs aren’t always dose-dependent—some occur unpredictably or at any dose, while others are dose-related.

An adverse drug reaction is a harmful, unintended effect that occurs when a drug is used at normal therapeutic doses. This captures the key idea: the reaction is not what was intended, and it causes harm, even though the drug is being taken as prescribed.

The other statements mix in elements of side effects or misstate how ADRs occur. Side effects can be predictable and mild, but that doesn’t define an adverse drug reaction. It’s not correct to say a side effect is always harmful. And ADRs aren’t always dose-dependent—some occur unpredictably or at any dose, while others are dose-related.