A 48-year-old woman is admitted with acute deep vein thrombosis (DVT) of the left lower limb confirmed on compression ultrasonography. She has no contraindications to anticoagulation. Which is the drug of choice for initial anticoagulation in acute DVT?

Explanation

## Initial Anticoagulation in Acute DVT ### First-Line Agent: Unfractionated Heparin (UFH) **Key Point:** Unfractionated heparin is the gold-standard initial anticoagulant for acute DVT because of its rapid onset, short half-life, reversibility, and suitability for dose adjustment and monitoring. ### Mechanism & Pharmacokinetics | Property | UFH | LMWH | Warfarin | |----------|-----|------|----------| | **Onset** | Immediate (IV) | 2–4 hours (SC) | 24–72 hours | | **Half-life** | 60–90 min | 4–6 hours | 36–42 hours | | **Monitoring** | aPTT | Anti-Xa level (optional) | INR | | **Reversibility** | Protamine sulfate | Partial (protamine) | Vitamin K, FFP | | **Renal clearance** | Minimal | Renal (caution in renal failure) | Hepatic | **High-Yield:** UFH allows rapid reversal with protamine sulfate if bleeding occurs, making it the safest choice in acute settings where intervention (thrombolysis, IVC filter, thrombectomy) may be needed. ### Dosing Regimen for UFH 1. **Loading dose:** 80 U/kg IV bolus 2. **Maintenance:** 18 U/kg/hour IV infusion 3. **Target aPTT:** 1.5–2.5 times baseline (or 46–70 seconds) 4. **Monitoring:** aPTT at 6 hours, then daily once therapeutic ### Transition to Warfarin - Start warfarin on **day 1** (overlap with UFH) - Continue UFH for minimum **5–7 days** and until INR 2–3 for 24 hours - Total anticoagulation duration: 3 months (provoked DVT) to indefinite (unprovoked) **Clinical Pearl:** In patients with heparin-induced thrombocytopenia (HIT) or heparin allergy, direct oral anticoagulants (DOACs: apixaban, rivaroxaban) or fondaparinux are alternatives, but UFH remains first-line in uncomplicated acute DVT. ### Why UFH Over LMWH in Acute DVT? - **Rapid reversibility** with protamine sulfate - **Shorter half-life** allows faster dose adjustment - **Renal clearance:** Minimal, safer in renal failure - **Intervention-ready:** Can be rapidly discontinued if thrombolysis or thrombectomy is needed - **Monitoring flexibility:** aPTT can be checked frequently **Mnemonic:** UFH = **U**rgent, **F**ast, **H**ighly reversible