Which of the following is an example of a non-immune mediated ADR mechanism?

• A. Immune responses
• B. Idiosyncratic responses
• C. On-target adverse effects
• D. Production of harmful immune responses

Answer: (C)

Non-immune mediated adverse drug reactions come from the drug’s pharmacologic action itself, not from the immune system. The best example here is an adverse effect that stems from the drug hitting its intended target in multiple tissues. These on-target adverse effects occur because the target is present in normal cells as well as in disease sites, so inhibiting or activating it can produce side effects that are predictable and often dose-dependent. For instance, blocking a receptor that exists throughout the body can cause adverse effects in healthy tissues simply due to that blockade, regardless of immune involvement.

Immune responses and harmful immune reactions describe ADRs driven by the immune system, such as hypersensitivity or autoimmunity, which is not the mechanism in on-target adverse effects. Idiosyncratic responses are unpredictable and not directly tied to the drug’s primary mechanism, so they don’t neatly illustrate a non-immune, pharmacologic adverse effect in the same straightforward way.