Which juice is least suitable for a patient taking warfarin due to interaction risk?

• A. Grapefruit
• B. Cranberry
• C. Orange
• D. Apple

Answer: (B)

The main idea here is how dietary components can affect warfarin’s effect. Cranberry juice is the one most consistently linked to increasing warfarin’s anticoagulant effect, which raises the risk of bleeding. It’s thought to interfere with the liver’s processing of warfarin (metabolism by cytochrome P450 enzymes) and may also affect factors related to vitamin K in the body, tipping the balance toward more anticoagulation. Because warfarin has a narrow therapeutic window, any factor that raises INR is a concern.

Grapefruit, orange, and apple juices do not show as clear or consistent a clinically significant interaction with warfarin as cranberry juice does, so they are considered less likely to cause a dangerous INR rise in most patients. In practice, patients on warfarin should maintain consistent vitamin K intake and be cautious with cranberry products, monitoring INR if intake changes.