A nurse is caring for a client who is taking warfarin and reports taking several new herbal supplements. The nurse should identify that which of the following supplements is contraindicated for concurrent use with warfarin?

A. Ginkgo biloba: Ginkgo biloba has antiplatelet properties and can increase the risk of bleeding when taken with warfarin. This herb can potentiate warfarin's anticoagulant effects, leading to an elevated INR and heightened risk of hemorrhage. B. Coenzyme Q10: Coenzyme Q10 may reduce the effectiveness of warfarin by promoting clotting. While this interaction requires monitoring, it does not increase bleeding risk like Ginkgo biloba and is not strictly contraindicated. C. Valerian: Valerian is a sedative herb used for insomnia and anxiety. It does not directly affect coagulation or warfarin metabolism, though it may pose sedation-related risks when combined with other CNS depressants. D. Probiotics: Probiotics generally do not interfere with warfarin's action. However, in rare cases, gut flora alteration might influence vitamin K synthesis, but this effect is typically minimal and not clinically significant.