Warfarin + TMP-SMX/metronidazole — ↑ anticoagulation
- Both inhibit S-warfarin CYP2C9 clearance
- INR/bleeding risk can rise quickly
- TMP-SMX also alters vitamin-K gut flora
- Consider an alternative antibiotic
- If combined: early/frequent INR checks
- Empiric warfarin reduction is often needed
Interaction at a glance
- INR/bleeding risk can rise quickly
- Empiric warfarin reduction is often needed
Management
- Both inhibit S-warfarin CYP2C9 clearance
- TMP-SMX also alters vitamin-K gut flora
- Consider an alternative antibiotic
- Empiric warfarin reduction is often needed
Clinical consequence
- INR/bleeding risk can rise quickly
Monitoring
- If combined: early/frequent INR checks
Self-check
- What is the main clinical risk of Warfarin + TMP-SMX/metronidazole?
INR/bleeding risk can rise quickly.
- Which enzyme or transporter is central to the Warfarin + TMP-SMX/metronidazole interaction?
CYP2C9.
Drugs in this interaction (4)
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