An adverse reaction is best defined as?

• A. The forecast of the likely course and outcome of a disease
• B. A painless condition
• C. An undesirable or harmful response to a medication or treatment
• D. The presence of blood in urine

Answer: (C)

An adverse reaction is an undesirable or harmful response to a medication or treatment. This ties the negative effect directly to the intervention being used, at normal dosing, and covers a range from mild to serious effects. It’s not about predicting how a disease will progress (that’s prognosis), nor about a condition being simply painless, nor about a symptom like blood in urine by itself. For example, a rash after starting a new drug or nausea with a medication illustrates an adverse reaction.