A nurse is preparing to administer warfarin to a client. Which of the following information should the nurse recognize prior to administering the medication?

Choice A reason: Activated partial thromboplastin time (aPTT) is used to monitor heparin therapy, not warfarin. Warfarin requires monitoring of the international normalized ratio (INR) and prothrombin time (PT) to assess its anticoagulant effect. Using aPTT for warfarin would not provide accurate information about the client's coagulation status. Choice B reason: NSAIDs should be avoided when a client is taking warfarin due to the increased risk of bleeding. NSAIDs can impair platelet function and cause gastrointestinal bleeding, which can be exacerbated by warfarin’s anticoagulant effects. Co-administration is contraindicated unless specifically directed and monitored by a healthcare provider. Choice C reason: Protamine sulfate is the antidote for heparin, not warfarin. The correct antidote for warfarin is vitamin K, which helps reverse its anticoagulant effects by promoting synthesis of clotting factors. Misidentifying the antidote could delay appropriate treatment in case of bleeding. Choice D reason: Observing the client for signs of hemorrhage is essential when administering warfarin. Warfarin increases the risk of bleeding due to its inhibition of vitamin K-dependent clotting factors. Nurses must monitor for signs such as bruising, hematuria, melena, and bleeding gums to ensure early detection and intervention.