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DOAC Drug Interactions — EECC MCQ

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ModerateArrhythmia & ElectrophysiologyDOAC Drug InteractionsEECC

A 55-year-old man with AF on rivaroxaban 20 mg daily is started on verapamil for rate control. The pharmacist flags a drug interaction. What is the concern?

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Correct answer: D — Verapamil may increase rivaroxaban exposure and bleeding risk

DOACs have clinically significant drug interactions, primarily through P-glycoprotein (P-gp) and CYP3A4 pathways. Rivaroxaban is a substrate of both P-gp and CYP3A4. Verapamil is a moderate P-gp inhibitor that increases rivaroxaban absorption, raising plasma levels by approximately 40%. While this does not routinely mandate dose reduction of rivaroxaban (unlike with dabigatran, which requires dose reduction from 150 to 110 mg bd with verapamil), the interaction should be considered in the context of other risk factors for bleeding (age, renal impairment, concomitant antiplatelets). The 2024 ESC AF Guidelines recommend awareness of P-gp and CYP3A4 interactions when prescribing DOACs. Strong dual P-gp/CYP3A4 inhibitors (ketoconazole, ritonavir) are contraindicated with rivaroxaban and apixaban.

Reference: ESC (2024): AF Guidelines; BNF DOAC Interactions: https://bnf.nice.org.uk/