A nurse is caring for a client who is prescribed warfarin. Which of the following actions should the nurse take?

A. Monitor the client's prothrombin time: Prothrombin time (PT), along with the international normalized ratio (INR), is used to monitor the anticoagulant effects of warfarin. Regular monitoring is essential to ensure therapeutic levels are maintained and to minimize the risk of bleeding. B. Increase the client's dietary intake of vitamin K: Vitamin K is the antidote to warfarin and reduces its effectiveness. Clients on warfarin are usually advised to maintain a consistent, not increased, intake of vitamin K-containing foods. Increasing dietary intake can counteract the drug’s anticoagulant effect and lead to subtherapeutic levels, which increases the risk of clot formation. C. Administer protamine sulfate if the client experiences an overdose: Protamine sulfate is the antidote for heparin, not warfarin. Warfarin overdose is treated with vitamin K and possibly fresh frozen plasma, making this an inappropriate response in the case of warfarin toxicity. D. Teach the client that St. John's wort increases the effects of the medication: St. John’s wort actually decreases the effectiveness of warfarin by inducing liver enzymes that metabolize the drug more rapidly. This can lead to a subtherapeutic INR and an increased risk of blood clots. The nurse should teach the client to avoid St. John's wort.