Warfarin¹

Dosing

• Warfarin Dosing Calculator
• Typically initiate at 5mg QD and adjust, consider 7.5mg QD or 2.5mg QD in special populations
  • 2.5mg
    • Elderly
    • Renal impairment
    • FHx of warfarin sensitivity
  • 7.5mg
    • Significant obesity
    • FHx of high warfarin doses
• 3mo of treatment
  • Bioprosthetic mitral valve
  • Provoked PE / DVT (no cancer)
  • MI induced LV thrombus
• Indefinite Treatment
  • A-fib
  • Mechanical Valves
  • Unprovoked PE / DVT
• Bridge until therapeutic INR for 24hr with therapeutic parenteral anticoagulant (usually enoxaparin)
• Adjust based on CYP2C9 and VKOR1 genotype, not usually relevant

Drug Interactions

Metabolized predominantly by CYP2C9, but also CYP1A2, 2C19, and 3A4.

Antidote^{1, 2}

• Elevated INR w/ Serious or Life-Threatening Bleed
  • Vit K 5-10mg slow IV bolus
    • Dilute in 50mL and infuse over 20min, or give no faster than 1mg/min
  • 4-factor PCC
    • INR > 6: 50 U/kg NTE 5000 U
    • INR 4-6: 35 U/kg NTE 3500 U
    • INR < 4: 25 U/kg NTE 2500 U
• INR > 10 w/o significant bleeding
  • Hold 1-2 doses
  • Vit K 2-2.5mg PO
  • Hold more and repeat Vit K as appropriate
• INR 4.5-10 w/o significant bleeding
  • Hold 1-2 doses
  • If high risk for bleeding, give Vit K 1-2mg PO
  • Monitor closely
• INR < 4.5
  • Lower dose or hold 1 dose

DOACs

Indication	Dose	Renal Adjustments	Notes
Apixaban
Non-Valvular A-fib	5mg BID	2.5mg BID if pt has 2 of the following ≥ 80yo SCr ≥ 1.5 ≤ 60kg	No bridge required
DVT / PE Treatment	10mg PO BID x7d, then 5mg BID		No bridge required
Indefinite DVT Prophylaxis	2.5mg PO BID		No bridge required
THA / TKA DVT Prophylaxis	2.5mg PO BID, starting 12-24htr after surgery x10-14d (TKA) or x30d (THA)		No bridge required
Rivaroxaban
Edoxaban
Dabigatran

Parenteral

References