Drug interactions
heparin + warfarin
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Overview
Additive anticoagulant effects increase major bleeding risk; combination should be limited to specific indications (e.g., bridging/ACS).
Mechanism of action
Pharmacodynamic: warfarin lowers vitamin K–dependent clotting factors; heparin potentiates antithrombin to inhibit thrombin/Factor Xa → impaired hemostasis.
Clinical management
Avoid routine co-therapy. If indicated, use lowest effective doses; monitor for bleeding, CBC/platelets, INR (warfarin) and aPTT or anti-Xa (heparin); reassess need frequently.
Drug reference
References
- Heparin Injection Prescribing Information — FDA Label
- Warfarin Sodium Tablets Prescribing Information — FDA Label
- Warfarin + Heparin Drug Interaction Monograph — Lexicomp
Frequently asked questions
Can I take heparin with warfarin?
The interaction is rated: Major. Additive anticoagulant effects increase major bleeding risk; combination should be limited to specific indications (e.g., bridging/ACS).
How serious is the interaction between heparin and warfarin?
The interaction is rated: Major. Evidence level: High.
How is the interaction between heparin and warfarin managed?
Avoid routine co-therapy. If indicated, use lowest effective doses; monitor for bleeding, CBC/platelets, INR (warfarin) and aPTT or anti-Xa (heparin); reassess need frequently.
Why do heparin and warfarin interact?
Pharmacodynamic: warfarin lowers vitamin K–dependent clotting factors; heparin potentiates antithrombin to inhibit thrombin/Factor Xa → impaired hemostasis.
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