Which of the following statements is true about Type B ADRs?

• A. They are unpredictable and usually not dose-dependent
• B. They are dose-related and predictable
• C. They are usually mild and self-limiting
• D. They occur only with penicillin administration

Answer: (A)

Type B adverse drug reactions are unpredictable and not dose-dependent. These idiosyncratic reactions often arise from rare genetic or immune-mediated factors, rather than the drug’s normal pharmacologic action. Because they don’t scale with dose, they can occur at typical or even low doses and may not be reproduced in most patients, making them hard to predict. They can range from hypersensitivity reactions to severe tissue injury, and their occurrence is not limited to a single drug. For example, immune-mediated reactions can happen with penicillin, but Type B reactions are not exclusive to penicillin. In contrast, other categories of ADRs are tied to the drug’s dose and predictable pharmacology, which is why the statement about unpredictability and non-dose-dependence is the defining trait of Type B ADRs.