Final answer:
Green tea can potentiate the effect of warfarin due to its high vitamin K content, which can reduce warfarin's efficacy and increase clotting risks. Patients are advised to monitor vitamin K intake, and pharmacogenomics can help tailor warfarin dosage.
Step-by-step explanation:
The nurse is caring for a client prescribed warfarin therapy, which is used to prevent blood clotting in various cardiovascular conditions. Of the substances listed, green tea may potentiate the effects of warfarin. Green tea contains large amounts of vitamin K, which can antagonize the inhibitory effect of warfarin on clotting factors, potentially leading to a reduced therapeutic effect and increased risk of clotting. Therefore, patients should monitor their intake of vitamin K-rich foods while on warfarin therapy. It is essential for patients and healthcare providers to be aware of the interactions between dietary supplements, such as St. John's wort and prescribed medications, particularly in complex treatments like warfarin therapy for atrial fibrillation. Pharmacogenomics can assist in tailoring warfarin treatment by identifying genetic variations that affect drug metabolism, hence adjusting dosage to prevent overdose complications while maintaining its efficacy.