## Initial Anticoagulation in Acute DVT **Key Point:** Unfractionated heparin (UFH) or low-molecular-weight heparin (LMWH) are the first-line agents for acute DVT. UFH is preferred in certain clinical scenarios due to its short half-life and reversibility. ### Why UFH is the Drug of Choice 1. **Rapid onset of action** — immediate anticoagulation via thrombin and Factor Xa inhibition 2. **Reversibility** — can be reversed with protamine sulfate if bleeding occurs 3. **Adjustable dosing** — allows aPTT-based titration in acute, unstable patients 4. **Renal clearance** — safe in severe renal impairment (unlike LMWH) 5. **Bridging agent** — used to transition to warfarin (oral anticoagulant for long-term management) ### Treatment Timeline ```mermaid flowchart TD A[Acute DVT confirmed]:::outcome --> B[Start UFH or LMWH]:::action B --> C[Achieve therapeutic aPTT/anti-Xa]:::action C --> D[Overlap with warfarin for 5-7 days]:::action D --> E[INR 2-3 achieved]:::decision E -->|Yes| F[Stop UFH, continue warfarin]:::action E -->|No| G[Continue overlap, recheck INR]:::action ``` **High-Yield:** UFH is the initial agent of choice; LMWH is an acceptable alternative in outpatient settings with normal renal function. Warfarin is NOT used as monotherapy for acute DVT because it takes 5–7 days to achieve therapeutic effect and carries a transient hypercoagulable state in the first 24–48 hours. **Clinical Pearl:** In massive iliofemoral DVT with limb-threatening complications (phlegmasia cerulea dolens), UFH allows rapid anticoagulation and is preferred over LMWH due to its reversibility and suitability for potential urgent thrombolysis or IVC filter placement. [cite:Harrison 21e Ch 297]
Sign up free to access AI-powered MCQ practice with detailed explanations and adaptive learning.