Warfarin

Warfarin was initially marketed as a pesticide for mice. A few years after being introduced, it was found to be effective and safe in preventing thrombosis and embolism. Warfarin was then approved to be a medication in early 1950s and has been used ever since. Common brand names are Coumadin, Warik, and Zyfarin. Warfarin is classified as a Coumarin derivative and an anticoagulant.

Indication for Warfarin

Warfarin is used as prophylaxis and treatment of venous thrombosis and pulmonary embolism. It is used in the treatment of thromboembolism associated with chronic atrial fibrillation. Warfarin is used as adjunct in treatment of coronary occlusion. It is also used as a prophylaxis and treatment of thromboembolic complications associated with cardiac valve replacement. Warfarin reduces risk of death, recurrent myocardial infarction, stroke, and embolization after myocardial infarction.

Warfarin can be used as a prohylaxis for recurrent cerebral embolism, myocardial reinfarction, and treatment adjunct in transient ischemic attacks.

Routes and Dosage of Warfarin

Alert: Dosage is highly individualized and is based on each individual’s prothrombin time (PT), INR (International Normalized Ratio).

Anticoagulant

PO: ADULTS, ELDERLY: Initially, 5-15 mg per day for 2-5 days, then adjust based on INR. MAINTENANCE: 2-10 mg per day. CHILDREN: Initially, 0.1-0.2 mg per kg. Maximum: 10 mg. MAINTENANCE: 0.05-0.34 mg/kg/day.

Usual Elderly Dosage

PO/IV: ADULTS: 2-5 mg per day (maintenance).

Action of Warfarin

Warfarin interferes with hepatic synthesis of vitamin K-dependent clotting factors, resulting in depletion of coagulation factors II, VII, IX, and X. Prevents further extension of formed existing clot, prevention of new clot formation, and secondary thromboembolic complications.

Side Effects and Adverse Reactions of Warfarin

Side Effects of Warfarin

GI distress: nausea, anorexia, abdominal cramps, and diarrhea.
Hypersensitivity reaction: dermatitis and urticaria. (Especially in patients sensitive to aspirin.)

Adverse Reactions of Warfarin

Bleeding complications ranging from local ecchymoses to major hemorrhage.
Hepatotoxicity
Blood dyscrasias
Necrosis
Vasculitis
Local thrombosis

Nursing Cosiderations for Clients Taking Warfarin

Cross-check dose with co-worker (nurse).
Determine INR prior to administration and daily following therapy initiation. When stabilized, follow with INR determinations ever 4-6 weeks.
Monitor INR reports diligently.
Assess hematocrit, platelet count, urine/stool culture for occult blood, AST, ALT, regardless of route administration.
Be alert to complaints of abdominal or back pain and severe headache.
Question for increase in amount of discharge during menses.
Assess area of thromboembolus for color and temperature.
Assess peripheral pulses; skin for bruises, and petechiae.
Check for excessive bleeding from minor cuts, and scratches.
Assess for gums for erythema and gingival bleeding.
Assess urine output for hematuria.
Scored tablets may be crushed.
Give without regard to food. If GI upset occurs, give with food.

Patient Teachings for Clients Taking Warfarin

Take medication exactly as prescribed.
Do not take or discontinue any other medication except on advice of physician.
Avoid alcohol, salicylates, and drastic dietary changes.
Do not change from one brand to another.
Consult with physician before surgery or dental work.
Urine may become red-orange.
Notify physician if bleeding, bruising, red-brown urine, or black stools occur.
Use electric razor and soft toothbrush to prevent bleeding.
Report any sign of coffee-ground colored vomitus and red-speckled mucus from cough.
Do not use any OTC medication without physician approval.

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