What does the term "adverse drug reaction" refer to?

• A. A beneficial response to a medication
• B. An unintended, harmful response to a medication
• C. A reaction to a drug that is expected
• D. A necessary side effect of treatment

Answer: (B)

Adverse drug reaction means an unintended, harmful response to a medication. It isn’t the intended therapeutic effect and can occur even when the drug is used correctly at normal doses. This distinguishes it from beneficial effects and from reactions that are merely expected or tolerated as part of treatment. While some side effects may be harmless or predictable, an adverse drug reaction is specifically undesired and harmful. Reactions can range from mild to severe, and recognizing them is key to patient safety.