What is the initial treatment and dosage for a patient with Deep Vein Thrombosis (DVT)?

Initial Treatment and Dosage for Deep Vein Thrombosis (DVT)

For acute DVT, initiate treatment with low-molecular-weight heparin (LMWH) at weight-adjusted doses: enoxaparin 1 mg/kg subcutaneously twice daily OR 1.5 mg/kg once daily, or dalteparin 200 units/kg subcutaneously once daily, preferred over unfractionated heparin. 1

Immediate Anticoagulation Strategy

Parenteral Anticoagulation Options (in order of preference):

LMWH (First-line):

• Enoxaparin: 1 mg/kg (100 units/kg) subcutaneously twice daily OR 1.5 mg/kg once daily 1
• Dalteparin: 200 units/kg subcutaneously once daily 1
• Once-daily dosing is suggested over twice-daily when the total daily dose is equivalent (convenience without compromising efficacy) 1

Fondaparinux (Alternative):

• Weight-based dosing: <50 kg: 5 mg; 50-100 kg: 7.5 mg; >100 kg: 10 mg subcutaneously once daily 1
• Preferred when LMWH is unavailable or in cases of heparin-induced thrombocytopenia 1

Unfractionated Heparin (UFH) - Reserve for specific situations:

• IV bolus: 80 units/kg, followed by continuous infusion at 18 units/kg/hour 2
• Adjust to maintain aPTT ratio 1.5-2.5 times control 1
• Use only when: severe renal impairment (CrCl <30 mL/min), high bleeding risk requiring rapid reversibility, hemodynamic instability, or morbid obesity 1, 3

Direct Oral Anticoagulants (DOACs) - Monotherapy Option:

Rivaroxaban (no initial parenteral therapy required):

• 15 mg orally twice daily with food for 21 days, then 20 mg once daily with food 4, 5
• This eliminates the need for bridging therapy 4

Apixaban (alternative DOAC):

• 10 mg orally twice daily for 7 days, then 5 mg twice daily 5, 6

Treatment Initiation Based on Clinical Suspicion

High clinical suspicion: Start parenteral anticoagulation immediately while awaiting diagnostic confirmation 1

Intermediate clinical suspicion: Start anticoagulation if diagnostic results delayed >4 hours 1

Low clinical suspicion: Withhold anticoagulation if test results expected within 24 hours 1

Transition to Long-Term Therapy (if using Warfarin)

Vitamin K antagonist (warfarin) initiation:

• Start warfarin on the same day as parenteral therapy (not delayed) 1
• Continue parenteral anticoagulation for minimum 5 days AND until INR ≥2.0 for at least 24 hours 1
• Target INR: 2.0-3.0 1, 7

Treatment Setting

Outpatient treatment is recommended for patients with adequate home circumstances (stable living conditions, family support, phone access, ability to return if deterioration, no severe symptoms) 1, 3

Special Populations

Cancer patients:

• LMWH at full dose (200 units/kg once daily) for 6 months is preferred over warfarin 1
• Continue anticoagulation as long as cancer remains active 1

Renal impairment (CrCl <30 mL/min):

• Avoid LMWH and fondaparinux due to accumulation risk 1, 2
• Use IV UFH with aPTT monitoring 1

Pregnancy:

• Use LMWH or UFH throughout pregnancy; avoid warfarin and DOACs 3, 5

Critical Pitfalls to Avoid

Do not use LMWH or fondaparinux in severe renal impairment (CrCl <25-30 mL/min) - drug accumulation causes bleeding risk 1, 2

Do not delay warfarin initiation - start same day as parenteral therapy to reduce total treatment time 1

Do not stop parenteral therapy prematurely - must continue minimum 5 days even if INR therapeutic earlier 1

Do not use IVC filters routinely - filters are NOT indicated when anticoagulation is feasible 1

Avoid DOACs in severe renal dysfunction - rivaroxaban and apixaban require dose adjustment or avoidance when CrCl <30 mL/min 5

Do not use loading doses of warfarin - start with estimated maintenance dose to reduce bleeding risk 7