Major
atorvastatin × warfarin
HMG-CoA reductase inhibitors (statins)×Vitamin K antagonist anticoagulants
Mechanism
Atorvastatin weakly inhibits CYP3A4 and CYP2C9. Clinically significant INR elevations are documented in a minority of cases, especially at 40–80 mg doses. The opposite – dose-dependent INR decrease – is also possible.
Management
Check INR 1–2 weeks after starting atorvastatin and after each dose change. Additional warfarin adjustment is usually not required but may be needed.
Sources
- Lexicomp: Lexicomp Drug Interactions (2024)— Wolters Kluwer Clinical Drug Information, Inc. Lexi-Interact Online, 2024
- Pharmaceutical Press: Stockley's Drug Interactions, 12th edition (2024)— Preston CL (ed.). Stockley's Drug Interactions. 12th ed. London: Pharmaceutical Press; 2024