A nurse is providing teaching to a client who has a new prescription for warfarin. Which of the following medications should the nurse instruct the client to avoid? (Select all that apply.)

Rationale: A. Ferrous sulfate: Ferrous sulfate is an iron supplement and does not directly interact with warfarin's anticoagulant effect. While some mild interactions are possible, it is not generally contraindicated unless specifically advised due to individual clinical conditions. B. Aspirin: Aspirin has antiplatelet effects and can increase the risk of bleeding when taken with warfarin. The combination enhances anticoagulation and significantly raises the chance of gastrointestinal or systemic bleeding. C. Naproxen: Naproxen is a nonsteroidal anti-inflammatory drug (NSAID) that can interfere with platelet function and irritate the gastrointestinal lining, increasing the risk of bleeding when combined with warfarin. D. Echinacea: Echinacea may interfere with liver enzyme activity and affect the metabolism of warfarin, potentially altering its effectiveness. Herbal supplements can cause unpredictable interactions and should generally be avoided while on warfarin. E. Dextromethorphan: Dextromethorphan is a common cough suppressant and does not have significant interactions with warfarin. It is generally considered safe for occasional use in clients taking anticoagulants.