skip to main content

H. pylori eradication warfarin interaction — GPhC CRA MCQ

Instant feedback + full explanation. One question, done properly.

ModerateGI TherapeuticsH. pylori eradication warfarin interactionGPhC CRA

A 55-year-old man taking warfarin for a prosthetic heart valve is prescribed a Helicobacter pylori eradication regimen of omeprazole, amoxicillin, and clarithromycin. What is the most important interaction to manage?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: A — Clarithromycin inhibits CYP3A4 and can increase warfarin's anticoagulant effect significantly

Clarithromycin is a potent CYP3A4 inhibitor and can significantly increase the anticoagulant effect of warfarin, increasing the risk of bleeding. Additionally, any broad-spectrum antibiotic course can alter gut flora and affect vitamin K synthesis, further potentiating warfarin. The patient's INR should be monitored closely during and shortly after the eradication course. The prescriber should be informed and a plan for enhanced INR monitoring arranged.

Reference: BNF Drug Interactions; NICE CKS H. pylori