An adverse drug reaction is

• A. Any noxious, unintended, and undesired effect that occurs at normal drug doses
• B. A predictable therapeutic effect
• C. An allergic reaction only
• D. An effect occurring only at high doses

Answer: (A)

An adverse drug reaction is any noxious, unintended, and undesired effect that occurs at normal drug doses. This means harm or discomfort can arise even when the drug is taken within its usual therapeutic range. It’s not simply a predictable therapeutic effect, which would be beneficial. It’s also broader than an allergic reaction, since many ADRs are nonallergic and arise from drug toxicity, intolerance, or interactions. And they don’t require high doses; ADRs can occur at standard doses due to individual sensitivity or other factors.