Warfarin Complications
Basics
Description
Description
- 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
Etiology
Etiology
- 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
- 15% of patients/yr:
- 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 INR | Decrease INR |
Multiple antibiotics | Carbamazepine |
NSAIDs | Barbiturates |
Amiodarone | Rifampin |
Propranolol | Haloperidol |
Prednisone | St. John's wort |
Cimetidine | High vitamin K foods |
Grapefruit, garlic | |
Ginkgo biloba |
Pregnancy Considerations
- Pregnancy class X
- Crosses the placenta causing spontaneous abortion and birth defects
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Citation
Schaider, Jeffrey J., et al., editors. "Warfarin Complications." 5-Minute Emergency Consult, 6th ed., Lippincott Williams & Wilkins, 2020. Emergency Central, emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307634/all/Warfarin_Complications.
Warfarin Complications. In: Schaider JJJ, Barkin RMR, Hayden SRS, et al, eds. 5-Minute Emergency Consult. Lippincott Williams & Wilkins; 2020. https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307634/all/Warfarin_Complications. Accessed November 4, 2024.
Warfarin Complications. (2020). In Schaider, J. J., Barkin, R. M., Hayden, S. R., Wolfe, R. E., Barkin, A. Z., Shayne, P., & Rosen, P. (Eds.), 5-Minute Emergency Consult (6th ed.). Lippincott Williams & Wilkins. https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307634/all/Warfarin_Complications
Warfarin Complications [Internet]. In: Schaider JJJ, Barkin RMR, Hayden SRS, Wolfe RER, Barkin AZA, Shayne PP, Rosen PP, editors. 5-Minute Emergency Consult. Lippincott Williams & Wilkins; 2020. [cited 2024 November 04]. 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
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