Top 300 Pharmacy Drug Cards

WARFARIN: Coumadin, Various

Class: Anticoagulant

Dosage Forms. Tablet: 1 mg, 2 mg, 2.5 mg, 3 mg, 4 mg, 5 mg, 6 mg, 7.5 mg, 10 mg


Common FDA Label Indication, Dosing, and Titration.

1. Multiple FDA-labeled indications, all dosed similarly, including atrial fibrillation; myocardial infarction; prosthetic cardiac valve component embolism; pulmonary embolism; thrombosis, postmyocardial infarction; venous thromboembolism: Initial, 2-5 mg po daily, adjust dose based on INR; usual maintenance 2-10 mg po daily

Off-Label Uses.

1. Antiphospholipid syndrome; cancer—venous thromboembolism: Initial, 2-5 mg po daily, adjust dose based on INR; usual maintenance 2-10 mg po daily

MOA. Warfarin prevents the conversion of vitamin K back to its active form from vitamin K epoxide. This impairs formation of the vitamin K–dependent clotting factors II, VII, IX, and X (prothrombin) and proteins C and S (physiologic anticoagulants).

Drug Characteristics: Warfarin


Medication Safety Issues: Warfarin


Drug Interactions: Warfarin


Adverse Reactions: Warfarin


Efficacy Monitoring Parameters. Measure initial INR after the first 2-3 doses and subsequently at intervals no longer than every 4 wk, once stable dose has been achieved; patients at high risk of bleeding require more frequent monitoring. INR target and therapeutic range depend on indication. Atrial fibrillation/atrial flutter: target 2.5 (range 2-3); prosthetic heart valves: target 2.5 (range 2-3); mechanical mitral or aortic valve: target 3 (range 2.5-3.5); myocardial infarction, ST segment elevation: target 3 (2.5-3.5, with aspirin); venous thromboembolism, prophylaxis, and treatment (including pulmonary embolism, DVT, hip/knee arthroplasty): target 2.5 (range 2-3).

Toxicity Monitoring Parameters. Signs/symptoms of bleeding, CBC, LFT, stool guaiac test.

Key Patient Counseling Points. Report signs/symptoms of hemorrhage, skin and tissue necrosis, and hepatitis. Avoid situations/activities in which cuts, bruising, or injury is likely to occur. Many significant drug-drug interactions, consult healthcare professional prior to new prescription or OTC use. Avoid alcohol, cranberry products, and drastic changes in vitamin K consumption from diet (cruciferous vegetables).

Clinical Pearls. Patients often managed in pharmacist run anticoagulation clinics. Consult local protocols. Excessive anticoagulation with warfarin can be corrected with vitamin K.

If you find an error or have any questions, please email us at Thank you!