A patient in the medical intensive care unit is receiving a heparin infusion for treatment of a pulmonary embolus. The nurse notices blood oozing from the IV site and pink urine in the indwelling catheter bag. Which medication does the nurse anticipate being ordered?

Protamine sulfate is the specific antidote for heparin toxicity. Heparin is an anticoagulant that works by potentiating antithrombin III, inhibiting thrombin and factor Xa. When a patient on heparin develops signs of excessive anticoagulation — such as oozing from an IV site and hematuria (indicated by pink urine) — the priority is to reverse the anticoagulant effect. Protamine sulfate is a positively charged molecule that binds directly to negatively charged heparin, forming a stable complex that neutralizes anticoagulant activity. Vitamin K is the antidote for warfarin overdose, not heparin; it restores clotting factor synthesis by the liver and would not rapidly reverse heparin's effect. Potassium chloride is an electrolyte replacement with no role in anticoagulant reversal. Vitamin E has antioxidant properties and some mild antiplatelet effects but is not used therapeutically to reverse anticoagulation. Distinguishing protamine sulfate (for heparin) from vitamin K (for warfarin) is a classic NCLEX-tested pharmacology concept that requires students to match antidotes to their specific anticoagulant drugs.