Drug interactions
Nafcillin + Warfarin
Severity: Major
Nafcillin and Warfarin: major interaction.
Last updated
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
Nafcillin is associated with reduced warfarin effect and warfarin resistance, sometimes requiring large dose increases. Once nafcillin is stopped, the INR can rise and cause over-anticoagulation.
What this interaction means in plain words
Nafcillin 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.
Why it happens
Induction of hepatic enzymes responsible for warfarin metabolism.
What to do
Monitor INR frequently during nafcillin therapy, increase the warfarin dose as needed, or use an alternative antibiotic. Reduce the warfarin dose and monitor INR closely after nafcillin is stopped.
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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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 Nafcillin with Warfarin?
MediHelp rates the interaction as major. Nafcillin 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. Nafcillin is associated with reduced warfarin effect and warfarin resistance, sometimes requiring large dose increases. Once nafcillin is stopped, the INR can rise and cause over-anticoagulation.
How serious is the interaction between Nafcillin 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: Monitor INR frequently during nafcillin therapy, increase the warfarin dose as needed, or use an alternative antibiotic. Reduce the warfarin dose and monitor INR closely after nafcillin is stopped.
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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