The action of Fondaparinux includes?
**Core Concept**
Fondaparinux is a synthetic anticoagulant that selectively inhibits Factor Xa, a key enzyme in the coagulation cascade. This action prevents the formation of thrombin and subsequent clot formation.
**Why the Correct Answer is Right**
Fondaparinux binds to antithrombin III, enhancing its ability to inhibit Factor Xa. This inhibition of Factor Xa disrupts the coagulation cascade, leading to reduced thrombin generation and decreased clot formation. Fondaparinux is particularly useful in preventing deep vein thrombosis and pulmonary embolism in patients undergoing orthopedic surgery.
**Why Each Wrong Option is Incorrect**
* **Option A:** Fondaparinux does not have a significant effect on Factor IIa (thrombin), which is the primary target of other anticoagulants like heparin and argatroban.
* **Option B:** Fondaparinux does not have a significant effect on Factor VIIa, which is involved in the initiation of the coagulation cascade but is not the primary target of Fondaparinux.
* **Option C:** Fondaparinux does not have a significant effect on platelet aggregation, which is a key component of clot formation but is not directly affected by Fondaparinux.
**Clinical Pearl / High-Yield Fact**
Fondaparinux has a longer half-life compared to low molecular weight heparins, allowing for once-daily dosing. It also has a lower risk of heparin-induced thrombocytopenia (HIT).
**Correct Answer: C. Inhibition of Factor Xa**