Drug interactions
Protein c + Warfarin
Severity: Major
Protein c and Warfarin: major interaction.
Last updated Sources: UK SmPC
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.
Summary
Warfarin lowers protein C and protein S early in therapy, before it reduces clotting factors, producing a transient hypercoagulable state. This can cause warfarin-induced skin necrosis, especially in patients with congenital protein C deficiency, so protein C replacement is used as cover during initiation.
What this interaction means in plain words
Protein c and Warfarin can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Protein c belongs to Cardiovascular; Warfarin belongs to Cardiovascular.
Why it happens
Warfarin rapidly depletes the short-half-life vitamin K-dependent protein C ahead of procoagulant factors, causing a transient prothrombotic imbalance.
What to do
Continue protein C replacement while starting warfarin until stable therapeutic anticoagulation is reached, and start warfarin at a low dose. Monitor INR and the skin closely.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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References
- CEPROTIN 1000 IU powder and solvent for solution for injection - SmPC sections 4.3/4.5 (names the partner; "Interaction with Vitamin K antagonists In patients starting treatment with oral anticoagulants belonging to the class of vitamin K antagonists (e.g. warfarin), ") — electronic medicines compendium (UK SmPC)
Other interactions of Warfarin
- Defibrotide + Warfarin Contraindicated
- Ketorolac + Warfarin Contraindicated
- Abciximab + Warfarin Major
- Acetylsalicylic acid + Warfarin Major
- Adagrasib + Warfarin Major
- Amiodarone + Warfarin Major
Frequently asked questions
Can I take Protein c with Warfarin?
MediHelp rates the interaction as major. Protein c and Warfarin can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Warfarin lowers protein C and protein S early in therapy, before it reduces clotting factors, producing a transient hypercoagulable state. This can cause warfarin-induced skin necrosis, especially in patients with congenital protein C deficiency, so protein C replacement is used as cover during initiation.
How serious is the interaction between Protein c and Warfarin?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Continue protein C replacement while starting warfarin until stable therapeutic anticoagulation is reached, and start warfarin at a low dose. Monitor INR and the skin closely.
What other medicines interact with Warfarin?
MediHelp also lists interactions of Warfarin with, for example, Defibrotide, Ketorolac, Abciximab. The full list is on the Warfarin page.
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