How do direct oral anticoagulants differ from warfarin in monitoring requirements?

• A. DOACs do not require routine INR monitoring; warfarin requires regular INR checks.
• B. DOACs require INR monitoring; warfarin does not.
• C. Both require INR monitoring
• D. DOACs are never monitored; warfarin is checked weekly.

Answer: (A)

Direct oral anticoagulants have a predictable, fixed effect and don’t rely on routine laboratory measurements to guide dosing. That means you don’t perform regular INR tests to adjust their anticoagulant effect. Warfarin, on the other hand, has a narrow therapeutic window and highly variable response between people because its activity is influenced by diet (especially vitamin K intake), other drugs, and genetic factors. Because of this variability, clinicians monitor the International Normalized Ratio (INR) to ensure the patient stays within the target range for their specific indication, adjusting the warfarin dose as needed. In practice, this translates to regular or frequent INR checks when starting therapy and as doses are adjusted, with ongoing monitoring to stay therapeutic. For DOACs, routine INR monitoring isn’t used; instead, renal function is often monitored to guide dosing, and specific tests are reserved for special situations where drug activity needs to be assessed.