💊 Warfarin (Warfarin Sodium)
Warfarin is an oral anticoagulant that works by inhibiting vitamin K-dependent clotting factors. It is used to prevent and treat venous thrombosis and pulmonary embolism, and thromboembolic complications associated with atrial fibrillation or cardiac valve replacement. It can cause major or fatal bleeding, so regular INR monitoring under your doctor's supervision is required.
In Arabic: وارفارين🏷️ Brand names & manufacturers
✅ What it is used for
- Prophylaxis and treatment of venous thrombosis and its extension, and pulmonary embolism
- Prophylaxis and treatment of thromboembolic complications associated with atrial fibrillation and/or cardiac valve replacement
- Reduction in the risk of death, recurrent myocardial infarction, and thromboembolic events such as stroke or systemic embolization after myocardial infarction
🧪 Active ingredient
The active substance is warfarin sodium, an anticoagulant that inhibits synthesis of the vitamin K-dependent clotting factors (II, VII, IX, X) as well as the anticoagulant proteins C and S.
🌿 Benefits
- Prevents extension of an established clot and secondary thromboembolic complications
- Reduces the risk of stroke and systemic embolization in the labeled indications
📝 How to use
- The dosing regimen is individualized for each patient by the doctor based on INR response and the condition treated; do not adjust the dose yourself
- Taken by mouth as tablets
- Regular INR testing is required; check with your doctor or pharmacist before starting, stopping, or changing the dose of any other medicine
- Duration of treatment depends on the condition and is decided by your doctor
💊 Dosage forms
- 1 mg tablets (pink)
- 2 mg tablets (lavender)
- 2½ mg tablets (green)
- 3 mg tablets (tan)
- 4 mg tablets (blue)
- 5 mg tablets (peach)
- 6 mg tablets (teal)
- 7½ mg tablets (yellow)
- 10 mg tablets (white)
⚠️ Common side effects
- Fatal and nonfatal hemorrhage from any tissue or organ (most common adverse reaction)
- Nausea, vomiting, diarrhea
- Taste perversion, abdominal pain, flatulence, bloating
- Rash, dermatitis, itching, hair loss
- Chills
🚨 Serious — seek medical help
- Major or fatal bleeding
- Tissue necrosis or gangrene of skin or other tissues
- Calciphylaxis (fatal and serious cases)
- Acute kidney injury
- Systemic atheroemboli and cholesterol microemboli
- Hypersensitivity reactions including hives and anaphylaxis
- Vasculitis
- Hepatitis and elevated liver enzymes
- Tracheal or tracheobronchial calcification
⛔ Do not use if
- Pregnancy (except in pregnant women with mechanical heart valves)
- Hemorrhagic tendencies or blood dyscrasias
- Recent or contemplated surgery of the central nervous system or eye, or traumatic surgery with large open surfaces
- Active ulceration or overt bleeding of the GI, genitourinary, or respiratory tract
- Central nervous system hemorrhage, cerebral aneurysms, dissecting aorta
- Pericarditis and pericardial effusions
- Bacterial endocarditis
- Threatened abortion, eclampsia, and preeclampsia
- Unsupervised patients with conditions associated with a high level of non-compliance
- Spinal puncture and other procedures with potential for uncontrollable bleeding
- Hypersensitivity to warfarin or any component (e.g., anaphylaxis)
- Major regional or lumbar block anesthesia
- Malignant hypertension
❗ Warnings & precautions
- Boxed warning: can cause major or fatal bleeding; bleeding is more likely within the first month
- Risk factors for bleeding include high-intensity anticoagulation (INR >4.0), age ≥65, highly variable INRs, history of GI bleeding, hypertension, cerebrovascular disease, anemia, malignancy, trauma, renal impairment, certain genetic factors, certain concomitant drugs, and long duration of therapy
- Perform regular INR monitoring; maintaining INR in the therapeutic range does not eliminate bleeding risk
- Drugs, dietary changes, and other factors affect INR; monitor INR more frequently when starting or stopping other drugs (including botanicals) or changing their doses
- Report signs and symptoms of bleeding
- Tissue necrosis, calciphylaxis, and atheroemboli: discontinue warfarin and consider alternatives
- Acute kidney injury may occur during episodes of excessive anticoagulation and hematuria
- Warfarin has no direct effect on an established thrombus and does not reverse ischemic tissue damage
- In heparin-induced thrombocytopenia (HIT), initial warfarin therapy has resulted in amputation and death; may be considered only after platelet count normalizes
🔄 Drug interactions
- Drugs that increase bleeding risk
- Antibiotics and antifungals
- Botanical (herbal) products
- Inhibitors and inducers of CYP2C9, 1A2, or 3A4: inhibitors may raise INR and inducers may lower it
- Corticosteroids (example of short-term drugs requiring more frequent INR monitoring)
- Cholestatic hepatitis has been associated with concomitant warfarin and ticlopidine
- Dietary changes can affect INR levels
- Consult your doctor or pharmacist before using any new drug or herbal product
🤰 Pregnancy
Warfarin is contraindicated in pregnancy except in pregnant women with mechanical heart valves at high risk of thromboembolism, where benefits may outweigh risks. It can cause fetal harm: first-trimester exposure caused a pattern of congenital malformations in about 5% of exposed offspring (warfarin embryopathy: nasal hypoplasia with or without stippled epiphyses and growth retardation), plus fatal fetal hemorrhage and increased risk of spontaneous abortion and fetal mortality. Tell your doctor immediately if you are pregnant or planning pregnancy.
🍼 Breastfeeding
Breastfed infants should be monitored for bruising or bleeding. Consult your doctor about breastfeeding during treatment.
🧒 Children
No pediatric information is included in the label text provided.
👴 Older adults
Age ≥65 is a risk factor for bleeding; patients at high risk of bleeding may benefit from more frequent INR monitoring and careful dose adjustment.
🌡️ Storage
Storage conditions are not included in the label text provided; follow the package instructions and your pharmacist's advice.
⏰ Missed dose
Missed-dose instructions are not included in the label text provided; consult your doctor or pharmacist and do not double the dose on your own.
🆘 Overdose
Bleeding (e.g., blood in stools or urine, excessive menstrual bleeding, black stools, petechiae, excessive bruising, persistent oozing from superficial injuries, unexplained fall in hemoglobin) is a manifestation of excessive anticoagulation. Treatment depends on INR level and presence of bleeding and may include stopping warfarin and giving vitamin K1; in urgent cases prothrombin complex concentrate, fresh frozen plasma, or activated Factor VII may be considered. Seek emergency medical help immediately.
💰 Price & brands in your area
Local prices are currently available for Palestine; more countries are coming. Ask your pharmacist for local price and alternatives.
📍 Find the nearest pharmacy
Your location is used only in your browser to show nearby pharmacies — we don't store it.
Open in Google Maps👨⚕️ For healthcare professionals
Mechanism of action
Warfarin inhibits synthesis of vitamin K-dependent clotting factors (II, VII, IX, X) and proteins C and S, thought to be via inhibition of the C1 subunit of the VKORC1 enzyme complex, reducing regeneration of vitamin K1 epoxide. Anticoagulant effect generally occurs within 24 hours, with peak effect possibly delayed 72–96 hours; a single dose lasts 2–5 days. It is essentially completely absorbed orally with peak concentration within 4 hours, volume of distribution about 0.14 L/kg, ~99% protein bound, and is eliminated almost entirely by hepatic CYP450 metabolism (S-enantiomer via CYP2C9; R-enantiomer via CYP1A2 and 3A4).
Labeled dosing
Dosing is individualized per patient based on INR response and the condition being treated, and is set by the doctor/pharmacist. Genotype can inform initial dose selection. Obtain daily INR on initiation until stable in range, then every 1 to 4 weeks. Target INR for venous thromboembolism and non-valvular AF is 2.5 (range 2.0–3.0). VTE secondary to a transient risk factor: 3 months; unprovoked DVT/PE: at least 3 months, then reassess risk-benefit; two unprovoked episodes: long-term treatment. INR >4.0 appears to provide no additional benefit and increases bleeding risk.
- Boxed warning: major or fatal bleeding risk; regular INR monitoring is required
- Bleeding is more likely within the first month
- Bleeding risk increases with INR >4.0, age ≥65, variable INRs, renal impairment, and certain genetic factors
- Vitamin K1 reversal reduces response to subsequent warfarin; heparin may be preferable if rapid re-anticoagulation is needed
- PCC and activated Factor VII carry increased thrombosis risk and should be reserved for exceptional or life-threatening bleeding
- Instruct patients with renal impairment to monitor INR frequently
- Report suspected adverse reactions to Amneal Pharmaceuticals at 1-877-835-5472 or FDA at 1-800-FDA-1088
🎓 Key points for students
- Class: vitamin K antagonist (oral anticoagulant)
- Mechanism: inhibits VKORC1, preventing activation of factors II, VII, IX, X and proteins C and S
- Monitored by INR; usual target 2.0–3.0 for VTE and non-valvular AF
- Peak effect is delayed 72–96 hours due to half-lives of clotting factors
- Key adverse effect: bleeding; rare serious ones include skin necrosis and calciphylaxis
- Metabolized by CYP2C9 (S) and CYP1A2/3A4 (R); response altered by inhibitors and inducers
- Main contraindications: pregnancy (except mechanical valves) and bleeding tendencies
- Reversal: vitamin K1, PCC, fresh frozen plasma, activated Factor VII in urgent cases
EME runs your whole clinic: appointments with WhatsApp reminders, patient files, finance & inventory, a patient portal and a members-price medical store — with your data isolated and protected.
Try EME free How we protect your data❓ FAQ
What is warfarin used for?
It is used to prevent and treat venous thrombosis and pulmonary embolism, thromboembolic complications of atrial fibrillation or cardiac valve replacement, and to reduce the risk of death, recurrent MI, and stroke or systemic embolization after myocardial infarction.
Why do I need regular INR tests?
The dose is individualized to your INR, and drugs, diet, and other factors affect it. Regular testing reduces the risk of serious bleeding but does not eliminate it.
Can warfarin be used during pregnancy?
It is contraindicated in pregnancy except in women with mechanical heart valves where benefits may outweigh risks, because it can cause birth defects and fetal bleeding. Talk to your doctor immediately.
What bleeding signs should I report?
Blood in stools or urine, black stools, heavy menstrual bleeding, excessive bruising, or persistent oozing from minor cuts. Contact your doctor right away.
Can I take other medicines or herbs with warfarin?
Many drugs, antibiotics, antifungals, and herbal products can interact with warfarin and change INR. Check with your doctor or pharmacist before starting or stopping any product.
⚕️ For education only — not a substitute for advice from your doctor or pharmacist. Do not start or stop any medicine without advice. Source: official FDA drug label via openFDA (2026-05), simplified. Updated: 2026-11-10.