2 Warfarin Therapy Free Online FlashCards

How does warfarin reduce clotting-factor activation?

Warfarin inhibits vitamin K epoxide reductase, reducing activation of vitamin K-dependent clotting factors.

Why does warfarin’s full antithrombotic effect take several days?

Existing clotting factors remain in circulation and are not immediately removed, so the full antithrombotic effect develops over several days.

Which laboratory measure guides warfarin dose adjustment?

Dose adjustment is guided by the prothrombin time expressed as the international normalized ratio (INR).

Is an INR goal of 2–3 universal for warfarin therapy?

No. An INR range of 2–3 is common for venous thromboembolism and atrial fibrillation, but some mechanical heart valves require a different target.

Why can’t one fixed warfarin starting dose suit every patient?

Dosing is individualized by INR response and the condition treated. Age, body weight, other medicines, and comorbidities can affect dose needs.

Which two genes can have variation that affects warfarin dose needs?

Genetic variation in CYP2C9 or VKORC1 can affect warfarin dose needs.

How can older age affect warfarin dosing?

Older adults may be more sensitive to warfarin and often need lower doses.

What should a patient do after starting a medicine that may interact with warfarin?

Promptly contact the anticoagulation clinician. New medicines can alter INR or bleeding risk, so closer monitoring or a dose change may be needed.

What dietary approach is recommended for vitamin K intake during warfarin therapy?

Aim for a consistent intake of vitamin K. Avoid sudden large dietary changes rather than avoiding nutritious foods altogether.

Should a patient double the next day’s warfarin dose after missing one?

Do not make up a missed dose by doubling the next day’s dose.

Why is warfarin generally avoided during pregnancy?

Warfarin can cause fetal harm, including congenital malformations and fetal bleeding, so it is generally contraindicated during pregnancy.

Is vitamin K routinely required for INR above 4.5 but below 10 without relevant bleeding?

Not always. For an INR above 4.5 but below 10 without clinically relevant bleeding, guidance suggests temporarily withholding warfarin rather than routinely adding vitamin K. Clinician assessment and follow-up INR testing are important.