Which of the following combinations does not cause a clinically significant drug interaction?

• A. Warfarin, Ramipril
• B. Digoxin, Amiodarone
• C. Lithium, Bendroflumethiazide
• D. Clarithromycin, Ramipril

Answer: (D)

Clinically significant interactions happen when one drug markedly changes the level or effect of another, either by altering metabolism/clearance (pharmacokinetic) or by producing a harmful additive effect (pharmacodynamic). The pairing of clarithromycin with ramipril does not create such a risk because ramipril is activated by esterases and not by CYP enzymes that clarithromycin inhibits, and there isn’t a shared adverse-effect threat that would be amplified here. In contrast, digoxin with amiodarone is a known interaction that raises digoxin levels and toxicity risk; lithium with bendroflumethiazide increases lithium levels and toxicity risk; while warfarin with ramipril is generally safe but can require monitoring due to individual variability. Therefore, clarithromycin with ramipril does not lead to a clinically significant interaction.