A Type A adverse drug reaction is characterized by

• A. Immune-mediated reaction
• B. Unrelated, random events
• C. Augmented, extensions of the drug's known pharmacology
• D. Drug interactions only

Answer: (C)

Type A adverse drug reactions are dose-related and arise from exaggeration of the drug’s own pharmacologic action. They are predictable because they reflect the normal mechanism of the drug, just amplified when the dose is higher or sensitivity is increased. That’s why this type is described as augmented extensions of the known pharmacology. For example, too much anticoagulant enhances bleeding, excessive insulin causes hypoglycemia, or high-dose NSAIDs irritate the stomach. Immune-mediated or idiosyncratic reactions (not dose-dependent) and reactions due to random interactions fall outside this category. So describing them as augmented extensions of the drug’s known pharmacology best captures Type A reactions.