Anticoagulation for Acute Deep Vein Thrombosis
For adults with acute DVT, start a direct oral anticoagulant (DOAC)—specifically apixaban, rivaroxaban, edoxaban, or dabigatran—immediately upon diagnosis, treat for a minimum of 3 months, and continue indefinitely if the DVT is unprovoked and bleeding risk is low-to-moderate. 1
Initial Anticoagulation Choice
DOACs (apixaban, rivaroxaban, edoxaban, dabigatran) are strongly preferred over warfarin for the first 3 months of treatment in all patients with acute DVT who do not have contraindications. 1
Apixaban and rivaroxaban are the most convenient first-line agents because they do not require parenteral lead-in therapy—start them immediately at diagnosis. 2, 3
Dabigatran and edoxaban require 5–10 days of parenteral anticoagulation (LMWH or fondaparinux) before the oral agent can be started. 3
DOAC Dosing (FDA-Approved Regimens)
Apixaban: 10 mg orally twice daily for 7 days, then 5 mg twice daily. 4
Rivaroxaban: 15 mg orally twice daily with food for 21 days, then 20 mg once daily with food. 5
Edoxaban and dabigatran: Require initial parenteral anticoagulation (LMWH or fondaparinux) for at least 5 days before starting the oral agent. 3
When Warfarin Must Be Used
If DOACs are contraindicated (e.g., severe renal impairment with CrCl <30 mL/min, antiphospholipid syndrome, pregnancy), use warfarin with parenteral bridging. 1, 2
Start warfarin on day 1 simultaneously with LMWH or fondaparinux—do not delay warfarin initiation. 2, 3
Continue parenteral therapy for at least 5 days and until INR ≥2.0 for ≥24 hours, then stop the parenteral agent. 1, 2
Target INR is 2.5 (range 2.0–3.0) throughout the entire treatment course. 1, 2
Minimum Treatment Duration
All patients with acute DVT require at least 3 months of therapeutic anticoagulation, regardless of whether the DVT is provoked or unprovoked. 1, 2
Stopping anticoagulation before 3 months is strongly discouraged because the risk of early recurrence and thrombus extension is unacceptably high. 1, 2
Duration Algorithm: Stop at 3 Months vs. Continue Indefinitely
Stop at 3 Months
DVT provoked by major transient risk factor (e.g., surgery, major trauma, hospitalization): Stop anticoagulation at 3 months because the annual recurrence risk after stopping is <1%. 1, 2
DVT provoked by minor transient risk factor (e.g., estrogen therapy, prolonged travel, minor injury): Stop at 3 months in most patients; extend only if bleeding risk is very low. 1, 2
Continue Indefinitely (No Scheduled Stop Date)
Unprovoked DVT with low-to-moderate bleeding risk: Continue anticoagulation indefinitely because the annual recurrence risk after stopping exceeds 5%, which outweighs bleeding risk. 1, 2
DVT with persistent risk factor (e.g., active cancer, chronic immobility, antiphospholipid syndrome): Continue indefinitely. 1, 2
Second unprovoked DVT: Lifelong anticoagulation is strongly recommended regardless of bleeding risk. 1
Reassess the risk-benefit ratio at least annually and at times of significant health status change. 1
Special Populations
Cancer-Associated DVT
Oral Factor Xa inhibitors (apixaban, edoxaban, or rivaroxaban) are preferred over LMWH for both initial and long-term treatment. 2, 3
Avoid rivaroxaban and edoxaban in patients with luminal GI malignancies due to increased bleeding risk; use apixaban or LMWH instead. 2
Continue anticoagulation indefinitely for as long as the malignancy remains active. 2, 3
Antiphospholipid Syndrome
Use warfarin (target INR 2.5) instead of DOACs because DOACs increase the risk of recurrent thrombosis in this population. 1, 2
Lifelong anticoagulation is indicated. 3
Severe Renal Impairment (CrCl <30 mL/min)
DOACs are contraindicated—use unfractionated heparin (UFH) followed by warfarin. 2
UFH dosing: 80 IU/kg IV bolus, then 18 IU/kg/h continuous infusion, adjusted by aPTT (target 1.5–2.5× control). 2
Start warfarin on day 1 and continue UFH for ≥5 days and until INR ≥2.0 for ≥24 hours. 2
Never use LMWH or fondaparinux in CrCl <30 mL/min due to drug accumulation and major bleeding risk. 2
Pregnancy
- LMWH is the only safe anticoagulant throughout pregnancy and postpartum—DOACs and warfarin are absolutely contraindicated. 3
Isolated Distal (Calf) DVT
For patients without severe symptoms or risk factors for extension: Serial imaging every 2 weeks for 2 weeks is preferred over immediate anticoagulation. 1
If the clot extends distally, start anticoagulation; if it extends proximally, anticoagulation is mandatory. 1
For patients with severe symptoms or risk factors for extension (e.g., active cancer, prior VTE, extensive clot burden): Start anticoagulation immediately. 1
If anticoagulation is started, treat for 3 months (same duration as proximal DVT). 1, 2
Inferior Vena Cava (IVC) Filters
IVC filters are recommended only when anticoagulation is absolutely contraindicated (e.g., active major bleeding, recent neurosurgery). 1, 3
Do not place IVC filters routinely in addition to anticoagulation—this is strongly discouraged. 1, 3
If a filter is placed temporarily, restart anticoagulation as soon as the bleeding risk resolves. 1, 3
Treatment Setting
Acute DVT can be managed safely in the outpatient setting when home circumstances are adequate (e.g., reliable follow-up, no severe comorbidities). 1, 2
Early ambulation is recommended over bed rest—prolonged immobilization does not reduce embolization risk and may worsen outcomes. 1
Common Pitfalls to Avoid
Do not stop anticoagulation before 3 months unless there is a major bleeding event—premature discontinuation dramatically increases recurrence risk. 1, 2
Do not use DOACs in antiphospholipid syndrome—they increase thrombosis recurrence; use warfarin instead. 1, 2, 3
Do not place IVC filters routinely—they are reserved for absolute anticoagulation contraindications only. 1, 3
Do not use LMWH, fondaparinux, or DOACs in severe renal impairment (CrCl <30 mL/min)—use UFH followed by warfarin. 2
Do not use rivaroxaban or edoxaban as first choice in cancer patients with luminal GI malignancies—use apixaban or LMWH instead. 2
Do not delay anticoagulation while awaiting diagnostic confirmation when clinical probability is intermediate or high—start empiric treatment immediately. 3