A nurse is monitoring a client who is receiving warfarin and has an INR of 4 (0.8 to 1.1). Which of the following medications should the nurse plan to administer?

Choice A rationale An INR (International Normalized Ratio) of 4.0 indicates that the client's blood is much thinner than the therapeutic range for most conditions (usually 2.0-3.0 for warfarin). This significantly increases the risk of bleeding. Vitamin K is the antidote for warfarin because it is essential for the synthesis of clotting factors (II, VII, IX, X) in the liver. Administering vitamin K reverses the anticoagulant effect of warfarin, reducing the risk of hemorrhage by promoting the production of functional clotting proteins. Choice B rationale Protamine sulfate is the antidote for heparin. It works by forming a stable ion pair with heparin, neutralizing its anticoagulant effects. It has no effect on the anticoagulant properties of warfarin, which acts by inhibiting vitamin K epoxide reductase, an enzyme crucial for the regeneration of active vitamin K necessary for clotting factor synthesis. Therefore, protamine is not indicated for warfarin overdose. Choice C rationale Calcium gluconate is used to treat hypocalcemia and magnesium toxicity. Calcium plays a vital role in numerous physiological processes, including bone health and muscle function, and is essential for blood coagulation. However, it does not directly counteract the effects of warfarin, which targets vitamin K-dependent clotting factors, and is not the appropriate antidote for an elevated INR. Choice D rationale Epinephrine is a potent vasoconstrictor and bronchodilator used in anaphylaxis, cardiac arrest, and severe asthma. It acts on alpha and beta-adrenergic receptors, leading to increased heart rate, blood pressure, and bronchodilation. It has no role in reversing the anticoagulant effects of warfarin and is not indicated for managing an elevated INR.