What are the characteristics of a Type F ADR?

• A. Common
• B. Uncommon
• C. Dose related; often caused by drug interactions
• D. End of use

Answer: (C)

Type F adverse drug reactions are about failure of therapy due to an interaction that changes how much drug is actually working in the body. The key idea is that the observed effect is reduced or lost because another drug alters the primary drug’s exposure, and this change is dose-related. If a second drug speeds up metabolism or reduces absorption, the primary drug’s plasma level can fall below what’s needed for the desired effect, so treatment fails rather than causing a new toxicity. Examples include enzyme-inducing medicines that lower levels of co‑administered drugs (like warfarin or oral contraceptives), leading to inadequate therapeutic response.