Quick facts
| Fact | Warfarin |
|---|---|
| Drug class[2] | Anticoagulant (vitamin K antagonist) |
| Used for[2] | Preventing and treating venous thrombosis and pulmonary embolism; clots linked to atrial fibrillation or heart valve replacement; lowering the risk of death, another heart attack and stroke after a heart attack |
| Boxed warning[2] | Major or fatal bleeding; monitor the INR regularly in every patient |
| INR target[1][2] | 2.0 to 3.0 for venous thromboembolism and nonvalvular atrial fibrillation; 2.5 to 3.5 for some mechanical heart valves |
| Check before giving[1] | INR results and signs of bleeding |
| Reversal[1][2] | Vitamin K1; prothrombin complex concentrate, fresh frozen plasma or activated factor VII may be considered when reversal is urgent |
| High-alert status[3] | On the ISMP high-alert list as an anticoagulant |
Before giving warfarin: check the INR and look for bleeding
- Review the INR before each dose. The label calls for a daily INR from the first dose until results are stable in range, then generally every 1 to 4 weeks.[1][2]
- An INR above 4.0 appears to add bleeding risk without extra benefit for most patients.[2]
- Look for bleeding: bruises on the arms or legs, or blood in the urine or stool.[1]
- Bleeding is more likely in the first month. Other risk factors include age 65 or older, past GI bleeding, hypertension, cerebrovascular disease, anemia, cancer, trauma, kidney impairment and highly variable INRs.[2]
- Expect extra INR checks whenever another drug is started, stopped or changed, including antibiotics, antifungals and herbal products.[2]
- Warfarin is contraindicated in pregnancy, except when a mechanical heart valve puts the patient at high risk of clots.[2]
Report bleeding signs, falls and skin changes right away
- Bleeding gums, nosebleeds, cuts that keep bleeding, unusual bruising, or heavier menstrual or vaginal bleeding.[2]
- Red or black stools, pink or brown urine, vomiting blood or vomit that looks like coffee grounds, or coughing up blood.[2]
- Headaches, dizziness, weakness, or any new pain, swelling or discomfort.[2]
- Any fall or injury, especially a blow to the head.[2]
- Pain and a purple, bruise-like rash on fatty areas such as the breasts, thighs, buttocks, hips or abdomen, which can be skin necrosis.[2]
- Sudden cool, painful, purple toes, which can come from cholesterol emboli.[2]
Teach steady vitamin K intake and no new drugs or herbals without asking
- Eat a normal, balanced diet with a consistent amount of vitamin K, and avoid drastic changes such as suddenly eating large amounts of leafy greens.[2]
- Don't start or stop any drug, including aspirin and other over-the-counter products, or any herbal product, without the provider's advice.[2]
- Some herbals add to bleeding (garlic, ginkgo); others can weaken warfarin (coenzyme Q10, St. John's wort, ginseng).[2]
- Open RN also teaches avoiding alcohol, cranberries and grapefruit, which can increase warfarin's effect.[1]
- Use an electric razor, avoid activities that could cause injury, and carry ID that says they take warfarin.[1][2]
- Tell every health care provider and dentist, especially before surgery or dental work.[2]
- If a dose is missed, take it as soon as possible the same day, and never double the next day's dose.[2]
Drill warfarin's INR monitoring, bleeding signs, and pregnancy restriction in the Antiplatelet and anticoagulant reasoning flashcard deck.
Browse flashcardsHow it shows up on nursing exams
- Warfarin is followed with the INR, and heparin with the aPTT.[2][4]
- Vitamin K reverses warfarin; protamine sulfate reverses heparin.[2][4]
- Diet teaching means a consistent vitamin K intake, with no big swings in leafy greens.[2]
- Neither warfarin nor heparin dissolves a clot that has already formed.[2][4]
Practice question
A 72-year-old patient who takes warfarin for atrial fibrillation comes to the emergency department with bleeding gums and a nosebleed that started 2 hours ago. INR is 6.1, blood pressure 138/84 mm Hg and heart rate 92/min. Which medication should the nurse expect the health care provider to prescribe to reverse the warfarin?
- A. Protamine sulfate
- B. Digoxin immune fab
- C. Vitamin K1
- D. Idarucizumab
Show the answer and why
Correct answer: C. Vitamin K1
- A. Incorrect. Protamine sulfate neutralizes heparin. It isn't the reversal agent for warfarin.
- B. Incorrect. Digoxin immune fab binds digoxin and is used for life-threatening digoxin toxicity.
- C. Correct. The warfarin label names vitamin K1, by mouth or by injection, along with stopping warfarin, to reverse excessive anticoagulation. Concentrates or plasma are kept for urgent, life-threatening bleeding.
- D. Incorrect. Idarucizumab is the specific reversal agent for dabigatran, a different anticoagulant. The warfarin label lists vitamin K1 for warfarin.
Sources for this question: [1][2][4][5]
Memory hook: Warfarin waits on the INR, and vitamin K brings it back down.