A nurse is teaching a client who has a new prescription for warfarin about medication interactions. Which of the following medications should the nurse instruct the client to avoid?

Choice A reason: Acetaminophen has minimal interaction with warfarin at standard doses, though high doses may affect INR. It is safer than ibuprofen, making this incorrect for medications to avoid. Choice B reason: Ibuprofen increases bleeding risk with warfarin by inhibiting platelets and causing gastrointestinal bleeding. Clients should avoid NSAIDs, making this the correct medication to instruct avoidance. Choice C reason: Ferrous sulfate does not significantly interact with warfarin. It may cause gastrointestinal upset but does not affect anticoagulation, making it incorrect for avoidance. Choice D reason: Omeprazole may slightly alter warfarin metabolism, but is not contraindicated. Monitoring INR suffices, making this incorrect compared to ibuprofen’s significant bleeding risk.