Which statement best describes warfarin interactions?

• A. Has minimal drug interactions
• B. Requires physician approval to take any other prescriptions or OTC meds
• C. Interacts only with antibiotics
• D. Works instantly and does not require monitoring

Answer: (B)

Warfarin has a narrow therapeutic range and is affected by many drug interactions because it works by inhibiting vitamin K–dependent clotting factors and is handled by liver enzymes. Because of this, adding any new prescription or OTC medication can unpredictably shift the INR, increasing bleeding risk or reducing anticoagulant effect. That’s why a clinician’s review and approval before taking other meds is essential, with dose adjustments and INR monitoring as needed. The other statements miss the reality: warfarin does not have minimal interactions, it does not interact only with antibiotics, and it does require ongoing monitoring and does not work instantly.