Drug interactions
trimethoprim-sulfamethoxazole + 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
↑ INR/bleeding risk.
Mechanism of action
CYP2C9 inhibition/displacement.
Clinical management
Avoid or reduce warfarin dose; close INR monitoring.
Drug reference
References
Frequently asked questions
Can I take trimethoprim-sulfamethoxazole with warfarin?
The interaction is rated: Major. ↑ INR/bleeding risk.
How serious is the interaction between trimethoprim-sulfamethoxazole and warfarin?
The interaction is rated: Major. Evidence level: High.
How is the interaction between trimethoprim-sulfamethoxazole and warfarin managed?
Avoid or reduce warfarin dose; close INR monitoring.
Why do trimethoprim-sulfamethoxazole and warfarin interact?
CYP2C9 inhibition/displacement.
Full monographs, dosing and an interaction checker in the MediHelp app
Open the complete reference, check multi-drug interactions and use dosing tools in the MediHelp app.