Which of the following is NOT a type of drug-drug interaction?

• A. Enzyme inhibition
• B. Enzyme induction
• C. Potentiation of pharmacologic effect
• D. Protein binding displacement

Answer: (D)

When studying drug-drug interactions, we classify them by how they change either drug levels or drug effects. Enzyme inhibition and enzyme induction are classic pharmacokinetic interactions: one drug slows down or speeds up the metabolism of another, respectively, leading to higher or lower concentrations and altered effects. Potentiation is a pharmacodynamic interaction, where two drugs together produce a greater effect than expected, without necessarily changing their concentrations.

Protein binding displacement can temporarily free more of a drug by freeing it from plasma proteins, but this isn’t normally treated as a separate, stand-alone type of drug-drug interaction in standard classifications. Its clinical significance can be variable and is not as consistently defined as the major categories above. So, among these options, protein binding displacement is not considered a distinct type of drug-drug interaction in this framework.