Type your tag names separated by a space and hit enter

Warfarin Complications

Warfarin Complications is a topic covered in the 5-Minute Emergency Consult.

To view the entire topic, please or purchase a subscription.

Emergency Central is a collection of disease, drug, and test information including 5-Minute Emergency Medicine Consult, Davis’s Drug, McGraw-Hill Medical’s Diagnosaurus®, Pocket Guide to Diagnostic Tests, and MEDLINE Journals created for emergency medicine professionals. Explore these free sample topics:

Emergency Central

-- The first section of this topic is shown below --



  • Most commonly prescribed oral anticoagulant
  • Inhibits vitamin K metabolism required for activation of factors II, VII, IX, and X
  • Blocks the coagulation cascade's extrinsic system and common pathway
  • Commonly used for venous thromboembolism and prevention of embolism with prosthetic heart valves or atrial fibrillation
  • Adjustments based on the international normalization ratio (INR)
    • Typical therapeutic range 2–3
    • 2.5–3.5 for mechanical valves and antiphospholipid syndromes
  • Contraindications include any condition in which the risk of hemorrhage or adverse reaction outweighs clinical benefit
    • Prior hypersensitivity
    • Skin reactions
    • Recent surgeries
    • Active or potential GI, intracerebral, or genitourinary bleeding
    • Fall risk


  • Bleeding complications:
    • 15% of patients/yr
      • 4.9% major bleeding events
      • Up to 0.8% fatal, most commonly intracranial hemorrhage (ICH)
    • Bleeding risk is directly related to INR
      • Increases dramatically above 4
  • Risk factors for nontherapeutic INR:
    • Age >75 yr
    • Hypertension, cerebrovascular disease, severe heart disease
    • Diabetes, renal insufficiency
    • Alcoholism or liver disease
    • Hypermetabolic states, fever
    • Hyperthyroidism
    • Cancer
    • Collagen vascular disease
    • Hereditary warfarin resistance
    • Cytochrome P450 polymorphism

Common Interactions

Increase INRDecrease INR
Multiple antibioticsCarbamazepine
PrednisoneSt. John wort
CimetidineHigh vitamin K foods
Grapefruit, garlic
Ginko biloba

Pregnancy Considerations
  • Pregnancy class X
  • Crosses the placenta causing spontaneous abortion and birth defects

-- To view the remaining sections of this topic, please or purchase a subscription --


Rosen, Peter, et al., editors. "Warfarin Complications." 5-Minute Emergency Consult, 5th ed., Lippincott Williams & Wilkins, 2016. Emergency Central, emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307634/all/Warfarin_Complications.
Warfarin Complications. In: Rosen P, Shayne P, Barkin AZ, et al, eds. 5-Minute Emergency Consult. 5th ed. Lippincott Williams & Wilkins; 2016. https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307634/all/Warfarin_Complications. Accessed April 24, 2019.
Warfarin Complications. (2016). In Rosen, P., Shayne, P., Barkin, A. Z., Wolfe, R. E., Hayden, S. R., Barkin, R. M., & Schaider, J. J. (Eds.), 5-Minute Emergency Consult. Available from https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307634/all/Warfarin_Complications
Warfarin Complications [Internet]. In: Rosen P, Shayne P, Barkin AZ, Wolfe RE, Hayden SR, Barkin RM, Schaider JJ, editors. 5-Minute Emergency Consult. Lippincott Williams & Wilkins; 2016. [cited 2019 April 24]. Available from: https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307634/all/Warfarin_Complications.
* Article titles in AMA citation format should be in sentence-case
TY - ELEC T1 - Warfarin Complications ID - 307634 ED - Rosen,Peter, ED - Shayne,Philip, ED - Barkin,Adam Z, ED - Wolfe,Richard E, ED - Hayden,Stephen R, ED - Barkin,Roger M, ED - Schaider,Jeffrey J, BT - 5-Minute Emergency Consult UR - https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307634/all/Warfarin_Complications PB - Lippincott Williams & Wilkins ET - 5 DB - Emergency Central DP - Unbound Medicine ER -