**Core Concept**
The initial therapy of documented deep venous thrombosis (DVT) involves anticoagulation to prevent further clot propagation and pulmonary embolism. This is crucial in postoperative cases where the risk of DVT is increased due to immobility, surgical trauma, and hypercoagulability.

**Why the Correct Answer is Right**
The correct initial therapy for DVT is anticoagulation with low molecular weight heparin (LMWH) or unfractionated heparin (UFH). This is based on the principle of inhibiting the coagulation cascade, specifically targeting the Factor Xa and thrombin pathways. LMWH and UFH work by binding to antithrombin III, which in turn inhibits Factor Xa and thrombin, preventing further clot formation. In postoperative cases, the risk of DVT is high, and prompt initiation of anticoagulation is essential to prevent complications.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because anticoagulation is the primary goal in the initial management of DVT, not anticoagulation reversal.
**Option B:** This option is incorrect because while antiplatelet agents like aspirin may be used in certain cases of DVT, they are not the initial therapy of choice.
**Option C:** This option is incorrect because anticoagulation with warfarin is typically initiated after 5-7 days of UFH or LMWH, not as the initial therapy.

**Clinical Pearl / High-Yield Fact**
It is essential to note that the initial therapy of DVT should be started within 24-48 hours of diagnosis, and the choice between LMWH and UFH depends on the patient's renal function, bleeding risk, and other factors.

**Correct Answer: C. Fondaparinux is not typically used as the initial treatment of DVT, it is used in some cases of Pulmonary Embolism.**