Which term describes an individual's unique hypersensitivity to a particular drug?

• A. Adverse drug effect
• B. Hypersensitivity
• C. Idiosyncrasy
• D. Antagonism

Answer: (C)

Idiosyncrasy describes an unusual, individual-specific response to a drug that cannot be predicted from the drug’s normal effects or typical dose response. This means the reaction is unique to that person, often due to genetic or metabolic differences, and it may manifest as a hypersensitivity that others do not experience. Because the reaction is not common, not dose-related, and not explained by the drug’s usual pharmacology, idiosyncrasy is the right term for an individual’s unique sensitivity. Adverse drug effects cover a broad range of harmful outcomes, not specifically the unpredictable, person-specific nature here. Hypersensitivity refers to immune-mediated allergic reactions, which can vary among individuals but aren’t inherently about a unique response in one person. Antagonism involves one drug blocking another’s effect, which isn’t about a patient’s hypersensitive reaction to a drug.