Warfarin

Vitamin K1-warfarin interaction effect. When warfarin levels are high, people have more risk of bleeding. Conversely, lower levels of warfarin lead to increased risk of blood clots. There is a narrow range where the benefits of warfarin are greater than the risks, its therapeutic window. Certain drugs, herbal medicines, and foods can interact with warfarin, increasing or decreasing a previously stable warfarin level.
Acyclic tautomer (left) and cyclic hemiketal tautomer (right)
3 mg (blue), 5 mg (pink) and 1 mg (brown) warfarin tablets (UK colours)
Warning label on a tube of rat poison laid on a dike of the Scheldt river in Steendorp, Belgium. The tube contains bromadiolone, a second-generation ("super-warfarin") anticoagulant.

Medication that is used as an anticoagulant .

- Warfarin

363 related topics

Relevance

Coagulation Cascade and Major Classes of Anticoagulants

Anticoagulant

Anticoagulants, commonly known as blood thinners, are chemical substances that prevent or reduce coagulation of blood, prolonging the clotting time.

Anticoagulants, commonly known as blood thinners, are chemical substances that prevent or reduce coagulation of blood, prolonging the clotting time.

Coagulation Cascade and Major Classes of Anticoagulants

Common anticoagulants include warfarin and heparin.

Blood plasma after the addition of tissue factor. The gel-like structure is strong enough to hold a steel ball.

Prothrombin time

Assay for evaluating the extrinsic pathway and common pathway of coagulation.

Assay for evaluating the extrinsic pathway and common pathway of coagulation.

Blood plasma after the addition of tissue factor. The gel-like structure is strong enough to hold a steel ball.
Vacutainer tube used for PT and PTT blood tests
Patient testing with microINR from iLine Microsystems
A Roche CoaguChek XS.

They are used to determine the clotting tendency of blood, in such things as the measure of warfarin dosage, liver damage, and vitamin K status.

DVT in the right leg with swelling and redness

Deep vein thrombosis

Type of venous thrombosis involving the formation of a blood clot in a deep vein, most commonly in the legs or pelvis.

Type of venous thrombosis involving the formation of a blood clot in a deep vein, most commonly in the legs or pelvis.

DVT in the right leg with swelling and redness
Swelling from fluid (edema) can result in "pitting" after pressure is applied. If this occurs only on one side, it raises the likelihood of DVT.
The iliac veins (in the pelvis) include the external iliac vein, the internal iliac vein, and the common iliac vein. The common femoral vein is below the external iliac vein. (It is labeled simply "femoral" here.)
Depiction of DVT
The coagulation system, often described as a "cascade", includes a group of proteins that regulate clotting. DVT risk can be altered by abnormalities in the cascade. The regulators, antithrombin (ᾳTHR) and activated protein C (APC), are shown in green above the clotting factors they affect.
500px
Upper extremity DVTs can occur in the subclavian, axillary, brachial, ulnar, and radial veins (pictured) and the jugular and brachiocephalic veins (not pictured). The cephalic and basilic veins, however, are superficial veins.
An IVC filter
The incision for a completed knee replacement surgery, a procedure that can precipitate DVT formation
An example of a compression stocking
Serena Williams has spoken at length about a frightening encounter she had with VTE while she was hospitalized in 2017.
Rudolf Virchow
Warfarin, a common vitamin K antagonist, was the mainstay of pharmacological treatment for about 50 years.
A CT image with red arrows indicating PE (grey) in the pulmonary arteries (white)|alt=A computed tomography image depicting PE in the pulmonary arteries
A case of phlegmasia cerulea dolens in the left leg|alt=Image showing marked discoloration of a leg with phlegmasia cerulea dolens
A depiction of a patent foramen ovale|alt=A drawing depicting a patent foramen ovale
An ultrasound with a blood clot visible in the left common femoral vein. (The common femoral vein is distal to the external iliac vein.)
Doppler ultrasonography showing absence of flow and hyperechogenic content in a clotted femoral vein (labeled subsartorial{{efn|Subsartorial is a proposed name for a section of the femoral vein.<ref>{{cite journal | vauthors = Häggström, M | title = Subsartorial vessels as replacement names for superficial femoral vessels | journal = International Journal of Anatomy, Radiology and Surgery | volume = 8 | issue = 1 | pages = AV01–02 | date = January 2019 | doi = 10.7860/IJARS/2019/40329:2458 | doi-access = free | url = http://www.ijars.net/articles/PDF/2458/40329_CE%5BRa1%5D_F(SHU)_PF1(A_SHU)_PFA(A_SHU)_PF2(AKA_SHU)_PN(SHU).pdf}}</ref>}}) distal to the branching point of the deep femoral vein.  When compared to this clot, clots that instead obstruct the common femoral vein (proximal to this branching point) cause more severe effects due to impacting a significantly larger portion of the leg.<ref name=IlioAHA>{{cite journal | vauthors = Jaff MR, McMurtry MS, Archer SL, Cushman M, Goldenberg N, Goldhaber SZ, Jenkins JS, Kline JA, Michaels AD, Thistlethwaite P, Vedantham S, White RJ, Zierler BK |display-authors = 6 | title = Management of massive and submassive pulmonary embolism, iliofemoral deep vein thrombosis, and chronic thromboembolic pulmonary hypertension: a scientific statement from the American Heart Association | journal = Circulation | volume = 123 | issue = 16 | pages = 1788–830 | date = April 2011 | pmid = 21422387 | doi = 10.1161/CIR.0b013e318214914f | doi-access=free }}</ref>
An abdominal CT scan demonstrating an iliofemoral DVT, with the clot in the right common iliac vein of the pelvis
The first rib, which is removed in a first rib resection surgery, is labeled 1 in this image
A venogram before catheter-directed thrombolysis for Paget–Schroetter syndrome, a rare and severe arm DVT shown here in a judo practitioner, with highly restricted blood flow shown in the vein
After treatment with catheter-directed thrombolysis, blood flow in the axillary and subclavian vein were significantly improved. Afterwards, a first rib resection allowed decompression. This reduces the risk of recurrent DVT and other sequelae from thoracic outlet compression.

Typical medications include rivaroxaban, apixaban, and warfarin.

A lung illustration depicting a pulmonary embolism as a thrombus (blood clot) that has travelled from another region of the body, causes occlusion of the pulmonary bronchial artery, leading to arterial thrombosis of the superior and inferior lobes in the left lung

Pulmonary embolism

Blockage of an artery in the lungs by a substance that has moved from elsewhere in the body through the bloodstream (embolism).

Blockage of an artery in the lungs by a substance that has moved from elsewhere in the body through the bloodstream (embolism).

A lung illustration depicting a pulmonary embolism as a thrombus (blood clot) that has travelled from another region of the body, causes occlusion of the pulmonary bronchial artery, leading to arterial thrombosis of the superior and inferior lobes in the left lung
A deep vein thrombosis as seen in the right leg is a risk factor for PE
A Hampton hump in a person with a right lower lobe pulmonary embolism
Selective pulmonary angiogram revealing clot (labeled A) causing a central obstruction in the left main pulmonary artery. ECG tracing shown at the bottom.
Electrocardiogram of a person with pulmonary embolism, showing sinus tachycardia of approximately 100 beats per minute, large S wave in Lead I, moderate Q wave in Lead III, inverted T wave in Lead III, and inverted T waves in leads V1 and V3.
Histopathology of a pulmonary artery from autopsy. It shows a fat embolism (seen as multiple empty globular spaces on this H&E stain since its processing dissolves fat). There is a bone marrow fragment in the middle, and multiple single hematopoietic cells in the blood, being evidence of fracture as the source of the embolism.
Used inferior vena cava filter.
Large saddle embolus seen in the pulmonary artery (white arrows).
On CT scan, pulmonary emboli can be classified according to the level along the arterial tree.
Segmental and subsegmental pulmonary emboli on both sides
CT pulmonary angiography showing a "saddle embolus" at the bifurcation of the main pulmonary artery and thrombus burden in the lobar arteries on both sides.
Pulmonary embolism (white arrow) that has been long-standing and has caused a lung infarction (black arrow) seen as a reverse halo sign.

Treatment is with anticoagulants such as heparin, warfarin or one of the direct-acting oral anticoagulants (DOACs).

CT scan of the brain showing a prior right-sided ischemic stroke from blockage of an artery. Changes on a CT may not be visible early on.

Stroke

Medical condition in which poor blood flow to the brain causes cell death.

Medical condition in which poor blood flow to the brain causes cell death.

CT scan of the brain showing a prior right-sided ischemic stroke from blockage of an artery. Changes on a CT may not be visible early on.
There are two main categories of strokes. Ischemic (top), typically caused by a blood clot in an artery (1a) resulting in brain death to the affected area (2a). Hemorrhagic (bottom), caused by blood leaking into or around the brain from a ruptured blood vessel (1b) allowing blood to pool in the affected area (2b) thus increasing the pressure on the brain.
A slice of brain from the autopsy of a person who had an acute middle cerebral artery (MCA) stroke
CT scan of an intraparenchymal bleed (bottom arrow) with surrounding edema (top arrow)
Illustration of an embolic stroke, showing a blockage lodged in a blood vessel.
Histopathology at high magnification of a normal neuron, and an ischemic stroke at approximately 24 hours on H&E stain: The neurons become hypereosinophilic and there is an infiltrate of neutrophils. There is slight edema and loss of normal architecture in the surrounding neuropil.
A CT showing early signs of a middle cerebral artery stroke with loss of definition of the gyri and grey white boundary
Dens media sign in a patient with middle cerebral artery infarction shown on the left. Right image after 7 hours.
12-lead ECG of a patient with a stroke, showing large deeply inverted T-waves. Various ECG changes may occur in people with strokes and other brain disorders.
Walking with an orthosis after a stroke
Stroke deaths per million persons in 2012
Hippocrates first described the sudden paralysis that is often associated with stroke.

Prevention includes decreasing risk factors, surgery to open up the arteries to the brain in those with problematic carotid narrowing, and warfarin in people with atrial fibrillation.

Leads aVL and aVF of an electrocardiogram showing atrial fibrillation. There are irregular intervals between heart beats. No P waves are seen and there is an erratic baseline between QRS complexes. The heart rate is about 125 beats per minute.

Atrial fibrillation

Abnormal heart rhythm (arrhythmia) characterized by rapid and irregular beating of the atrial chambers of the heart.

Abnormal heart rhythm (arrhythmia) characterized by rapid and irregular beating of the atrial chambers of the heart.

Leads aVL and aVF of an electrocardiogram showing atrial fibrillation. There are irregular intervals between heart beats. No P waves are seen and there is an erratic baseline between QRS complexes. The heart rate is about 125 beats per minute.
Normal rhythm tracing (top) Atrial fibrillation (bottom)
How a stroke can occur during atrial fibrillation
Non-modifiable risk factors (top left box) and modifiable risk factors (bottom left box) for atrial fibrillation. The main outcomes of atrial fibrillation are in the right box. BMI=Body Mass Index.
A 12-lead ECG showing atrial fibrillation at approximately 132 beats per minute
Diagram of normal sinus rhythm as seen on ECG. In atrial fibrillation the P waves, which represent depolarization of the top of the heart, are absent.
ECG of atrial fibrillation (top) and normal sinus rhythm (bottom). The purple arrow indicates a P wave, which is lost in atrial fibrillation.
3D Medical Animation still shot of Left Atrial Appendage Occlusion

Anti-clotting medications include warfarin and direct oral anticoagulants.

Diagram of a thrombus (blood clot) that has blocked a blood vessel valve

Thrombus

Final product of the blood coagulation step in hemostasis.

Final product of the blood coagulation step in hemostasis.

Diagram of a thrombus (blood clot) that has blocked a blood vessel valve
Illustration comparing normal artery with diseased artery with a blood clot.
Animation of the formation of an occlusive thrombus in a vein. A few platelets attach themselves to the valve lips, constricting the opening and causing more platelets and red blood cells to aggregate and coagulate. Coagulation of unmoving blood on both sides of the blockage may propagate a clot in both directions.
Micrograph showing a thrombus (center of image) within a blood vessel of the placenta. H&E stain.
Illustration depicting thrombus formation over arterial plaque.
Composition of a fresh thrombus at microscopy, showing nuclear debris in a background of fibrin and red blood cells.

Heparin and warfarin are used to inhibit the formation and growth of existing thrombi, with the former used for acute anticoagulation while the latter is used for long-term anticoagulation.

Different types of artificial heart valves

Artificial heart valve

One-way valve implanted into a person's heart to replace a heart valve that is not functioning properly .

One-way valve implanted into a person's heart to replace a heart valve that is not functioning properly .

Different types of artificial heart valves
3D Medical Animation still shot of Artificial Heart Valve
Caged ball valve
tilting-disc valve
Bileaflet valve
3D Rendering of Mechanical Valve
3D Rendering of Mechanical Valve (St. Francis model)

People with mechanical valves need to take anticoagulants (blood thinners), such as warfarin, for the rest of their life.

A bleeding wound in the finger

Bleeding

Blood escaping from the circulatory system from damaged blood vessels.

Blood escaping from the circulatory system from damaged blood vessels.

A bleeding wound in the finger
A subconjunctival hemorrhage is a common and relatively minor post-LASIK complication.
Micrograph showing abundant hemosiderin-laden alveolar macrophages (dark brown), as seen in a pulmonary hemorrhage. H&E stain.

In addition to NSAID-related bleeding, another common cause of bleeding is that related to the medication, warfarin ("Coumadin" and others).

Kekulé's 1872 modification of his 1865 theory, illustrating rapid alternation of double bonds Critics pointed out a problem with Kekulé's original (1865) structure for benzene: Whenever benzene underwent substitution at the ortho position, two distinguishable isomers should have resulted, depending on whether a double bond or a single bond existed between the carbon atoms to which the substituents were attached; however, no such isomers were observed.  In 1872, Kekulé suggested that benzene had two complementary structures and that these forms rapidly interconverted, so that if there were a double bond between any pair of carbon atoms at one instant, that double bond would become a single bond at the next instant (and vice versa).  To provide a mechanism for the conversion process, Kekulé proposed that the valency of an atom is determined by the frequency with which it collided with its neighbors in a molecule.  As the carbon atoms in the benzene ring collided with each other, each carbon atom would collide twice with one neighbor during a given interval and then twice with its other neighbor during the next interval.  Thus, a double bond would exist with one neighbor during the first interval and with the other neighbor during the next interval.  Therefore, between the carbon atoms of benzene there were no fixed (i.e., constant) and distinct single or double bonds; instead, the bonds between the carbon atoms were identical.  See pages 86–89  of Auguste Kekulé (1872) "Ueber einige Condensationsprodukte des Aldehyds" (On some condensation products of aldehydes), Liebig's Annalen der Chemie und Pharmacie, 162(1): 77–124, 309–320.  From p. 89:  "Das einfachste Mittel aller Stöße eines Kohlenstoffatoms ergiebt sich aus der Summe der Stöße der beiden ersten Zeiteinheiten, die sich dann periodisch wiederholen.  … man sieht daher, daß jedes Kohlenstoffatom mit den beiden anderen, … daß diese Verschiedenheit nur eine scheinbare, aber keine wirkliche ist." (The simplest average of all the collisions of a carbon atom [in benzene] comes from the sum of the collisions during the first two units of time, which then periodically repeat.  … thus one sees that each carbon atom collides equally often with the two others against which it bumps, [and] thus stands in exactly the same relation with its two neighbors.  The usual structural formula for benzene expresses, of course, only the collisions that occur during one unit of time, thus during one phase, and so one is led to the view [that] doubly substituted derivatives [of benzene] must be different at positions 1,2 and 1,6 [of the benzene ring].  If the idea [that was] just presented—or a similar one—can be regarded as correct, then [it] follows therefrom that this difference [between the bonds at positions 1,2 and 1,6] is only an apparent [one], not a real [one].)

Coumarin

Aromatic organic chemical compound with formula C9H6O2.

Aromatic organic chemical compound with formula C9H6O2.

Kekulé's 1872 modification of his 1865 theory, illustrating rapid alternation of double bonds Critics pointed out a problem with Kekulé's original (1865) structure for benzene: Whenever benzene underwent substitution at the ortho position, two distinguishable isomers should have resulted, depending on whether a double bond or a single bond existed between the carbon atoms to which the substituents were attached; however, no such isomers were observed.  In 1872, Kekulé suggested that benzene had two complementary structures and that these forms rapidly interconverted, so that if there were a double bond between any pair of carbon atoms at one instant, that double bond would become a single bond at the next instant (and vice versa).  To provide a mechanism for the conversion process, Kekulé proposed that the valency of an atom is determined by the frequency with which it collided with its neighbors in a molecule.  As the carbon atoms in the benzene ring collided with each other, each carbon atom would collide twice with one neighbor during a given interval and then twice with its other neighbor during the next interval.  Thus, a double bond would exist with one neighbor during the first interval and with the other neighbor during the next interval.  Therefore, between the carbon atoms of benzene there were no fixed (i.e., constant) and distinct single or double bonds; instead, the bonds between the carbon atoms were identical.  See pages 86–89  of Auguste Kekulé (1872) "Ueber einige Condensationsprodukte des Aldehyds" (On some condensation products of aldehydes), Liebig's Annalen der Chemie und Pharmacie, 162(1): 77–124, 309–320.  From p. 89:  "Das einfachste Mittel aller Stöße eines Kohlenstoffatoms ergiebt sich aus der Summe der Stöße der beiden ersten Zeiteinheiten, die sich dann periodisch wiederholen.  … man sieht daher, daß jedes Kohlenstoffatom mit den beiden anderen, … daß diese Verschiedenheit nur eine scheinbare, aber keine wirkliche ist." (The simplest average of all the collisions of a carbon atom [in benzene] comes from the sum of the collisions during the first two units of time, which then periodically repeat.  … thus one sees that each carbon atom collides equally often with the two others against which it bumps, [and] thus stands in exactly the same relation with its two neighbors.  The usual structural formula for benzene expresses, of course, only the collisions that occur during one unit of time, thus during one phase, and so one is led to the view [that] doubly substituted derivatives [of benzene] must be different at positions 1,2 and 1,6 [of the benzene ring].  If the idea [that was] just presented—or a similar one—can be regarded as correct, then [it] follows therefrom that this difference [between the bonds at positions 1,2 and 1,6] is only an apparent [one], not a real [one].)

By inhibiting synthesis of vitamin K, a related compound is used as the prescription drug warfarin – an anticoagulant – to inhibit formation of blood clots, deep vein thrombosis, and pulmonary embolism.