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 can increase the risk of bleeding when taken with warfarin by inhibiting platelet aggregation and enhancing anticoagulant effects. Concurrent use requires careful monitoring or avoidance to prevent serious hemorrhagic events. B. Probiotics: Probiotics generally do not affect coagulation or interfere with warfarin therapy. They are considered safe for concurrent use and primarily support gut health. C. Coenzyme Q10: Coenzyme Q10 may actually reduce the effectiveness of warfarin by promoting clotting, but it does not directly increase bleeding risk. Monitoring may be required, but it is not strictly contraindicated. D. Valerian: Valerian is primarily a sedative and does not have significant anticoagulant effects. It does not directly interact with warfarin, although clients should be monitored for additive CNS depression if used with other sedatives.