What is the antidote for heparin overdose?

Protamine sulfate is the antidote for heparin overdose because it directly neutralizes the effects of heparin, a potent anticoagulant. Heparin works by enhancing the activity of antithrombin III, which in turn inhibits thrombin and factor Xa, preventing blood clot formation. When there is an overdose of heparin, resulting in an increased risk of bleeding, administering protamine sulfate helps reverse this anticoagulant effect by binding to heparin and forming a stable complex. This action effectively restores normal coagulation levels and reduces the risk of severe bleeding complications associated with high heparin concentrations in the bloodstream.

Other options listed do not serve as effective antidotes for heparin. Vitamin K is used for reversing anticoagulation due to warfarin, activated charcoal is a treatment for some types of poisoning and drug overdoses but is not specific to heparin, and calcium gluconate is primarily used to treat hypocalcemia or mitigate the effects of hyperkalemia, rather than reversing heparin's effects. Thus, the use of protamine sulfate is essential in the management of heparin overdose scenarios.