Antagonist of heparin is :
**Core Concept**
Heparin is a potent anticoagulant medication that inhibits thrombin formation by activating antithrombin III, thereby preventing blood clot formation. The need for an antagonist arises when managing heparin-induced thrombocytopenia (HIT), a serious side effect of heparin therapy.
**Why the Correct Answer is Right**
Protamine sulfate is a positively charged protein that binds to the negatively charged heparin molecule, effectively neutralizing its anticoagulant activity. This binding reaction is highly specific, with protamine sulfate having a 1:1 molar ratio with heparin. The complex formed between protamine and heparin is then rapidly cleared from the bloodstream, terminating heparin's anticoagulant effect. This mechanism is crucial in managing HIT and reversing heparin-induced anticoagulation.
**Why Each Wrong Option is Incorrect**
**Option A:** Warfarin - Warfarin is an oral anticoagulant that inhibits vitamin K-dependent clotting factors, but it does not reverse heparin's effects.
**Option B:** Phospholipids - Phospholipids are components of cell membranes and are not involved in reversing heparin's anticoagulant activity.
**Option C:** Plasminogen activators - Plasminogen activators, such as tissue plasminogen activator (tPA), are used to dissolve existing blood clots, but they do not reverse heparin's effects.
**Clinical Pearl / High-Yield Fact**
When reversing heparin's anticoagulant effect, it is essential to administer protamine sulfate slowly (over 10 minutes) to avoid a sudden drop in blood pressure.
**Correct Answer: C. Protamine sulfate**