Which of the following is the antidote for heparin?

• A. Protamine sulfate
• B. Vitamin K
• C. Aminocaproic acid
• D. Vitamin C

Answer: (A)

Protamine sulfate is the antidote for heparin. Heparin works by enhancing antithrombin III to inactivate thrombin and factor Xa, stopping clot formation. Protamine sulfate, a positively charged molecule, binds to the negatively charged heparin and neutralizes its anticoagulant effect, allowing normal clotting to resume. This reversal is most effective when given promptly after heparin exposure; dosing is typically about 1 mg of protamine per 100 units of heparin given, with adjustments based on timing and amount of heparin received. In practice, low-molecular-weight heparin may be partially reversed by protamine but not completely. Watch for potential adverse effects like hypotension, bradycardia, or rare anaphylactoid reactions, so administer IV slowly and monitor closely. Vitamin K reverses warfarin, not heparin; aminocaproic acid is used in different bleeding scenarios, and vitamin C has no role in reversing heparin’s effects.