Anticoagulant

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Anticoagulant
Drug class
Coagulation Cascade and Major Classes of Anticoagulants.png
Coagulation cascade and major classes of anticoagulants
Class identifiers
ATC code B01
External links
MeSH D00534-class
Legal status
In Wikidata

An anticoagulant, commonly known as a blood thinner, is a chemical substance that prevents or reduces the coagulation of blood, prolonging the clotting time. [1] Some occur naturally in blood-eating animals, such as leeches and mosquitoes, which help keep the bite area unclotted long enough for the animal to obtain blood. [2] [3]

Contents

As a class of medications, anticoagulants are used in therapy for thrombotic disorders. [4] Oral anticoagulants (OACs) are taken by many people in pill or tablet form, and various intravenous anticoagulant dosage forms are used in hospitals. [5] [6] Some anticoagulants are used in medical equipment, such as sample tubes, blood transfusion bags, heart–lung machines, and dialysis equipment. [7] [8] One of the first anticoagulants, warfarin, was initially approved as a rodenticide. [9]

Anticoagulants are closely related to antiplatelet drugs and thrombolytic drugs by manipulating the various pathways of blood coagulation. [10] Specifically, antiplatelet drugs inhibit platelet aggregation (clumping together), whereas anticoagulants inhibit specific pathways of the coagulation cascade, which happens after the initial platelet aggregation but before the formation of fibrin and stable aggregated platelet products. [11] [12]

Common anticoagulants include warfarin and heparin. [13]

Medical uses

The use of anticoagulants is a decision based on the risks and benefits of anticoagulation. [14] The biggest risk of anticoagulation therapy is the increased risk of bleeding. [15] In otherwise healthy people, the increased risk of bleeding is minimal, but those who have had recent surgery, cerebral aneurysms, and other conditions may have too great a risk of bleeding. [16] [17] Generally, the benefit of anticoagulation is preventing or reducing the progression of a thromboembolic disease. [18] Some indications for anticoagulant therapy that are known to have benefit from therapy include:

In these cases, anticoagulation therapy prevents the formation or growth of dangerous clots. [30]

The decision to begin therapeutic anticoagulation often involves the use of multiple bleeding risk predictable outcome tools as non-invasive pre-test stratifications due to the potential for bleeding while on blood thinning agents. [15] Among these tools are HAS-BLED, [31] ATRIA, [32] HEMORR2HAGES, [33] and CHA2DS2-VASc. [34] The risk of bleeding using the risk assessment tools above must then be weighed against thrombotic risk to formally determine the patient's overall benefit in starting anticoagulation therapy. [35]

There is no evidence to indicate that adding anticoagulant therapy to standard treatment has a benefit for people with cerebral small vessel disease but not dementia, and there is an increased risk of a person with this disease experiencing a bleed with this approach. [36]

Adverse effects

The most serious and common adverse side effects associated with anticoagulants are increased risk of bleeding, both nonmajor and major bleeding events. [37] The bleeding risk depends on the class of anticoagulant agent used, the patient's age, and pre-existing health conditions. Warfarin has an estimated incidence of bleeding of 15-20% per year and a life-threatening bleeding rate of 1-3% per year. [38] Newer non-vitamin K antagonist oral anticoagulants appear to have fewer life-threatening bleeding events than warfarin. [39] [40] Additionally, patients aged 80 years or more may be especially susceptible to bleeding complications, with a rate of 13 bleeds per 100 person-years. [41] Bleeding risk is especially important to consider in patients with renal impairment and NOAC therapy because all NOACs, to some extent, are excreted by the kidneys. [42] Thus, patients with renal impairment may be at higher risk of increased bleeding. [43]

In people with cancer, a systematic review has found warfarin had no effect on death rate or the risk of blood clots. [44] However, it did increase the risk of major bleeding in 107 more people per 1000 population and minor bleeding in 167 more people per 1000 population. [44] Apixaban had no effect on mortality, recurrence of blood clots in blood vessels, or major or minor bleeding. However, this finding comes only from one study. [44]

Nonhemorrhagic adverse events are less common than hemorrhagic adverse events but should still be monitored closely. [39] Nonhemorrhagic adverse events of warfarin include skin necrosis, limb gangrene, and purple toe syndrome. [45] Skin necrosis and limb gangrene are most commonly observed on the third to eighth day of therapy. [46] [47] The exact pathogenesis of skin necrosis and limb gangrene is not completely understood but it is believed to be associated with warfarin's effect on inhibiting the production of protein C and protein S. [48] [49] Purple toe syndrome typically develops three to eight weeks after initiation of warfarin therapy. [50] [51] Other adverse effects of warfarin are associated with depletion of vitamin K, which can lead to inhibition of G1a proteins and growth arrest-specific gene 6, which can lead to increased risk of arterial calcification and heart valve, especially if too much Vitamin D is present. [52] [53] Warfarin's interference with G1a proteins has also been linked to abnormalities in fetal bone development in mothers who were treated with warfarin during pregnancy. [54] [55] Long-term warfarin and heparin usage have also been linked to osteoporosis. [56] [45]

Another potentially severe complication associated with heparin use is called heparin-induced thrombocytopenia (HIT). [57] There are two distinct types: HIT 1) immune-mediated and 2) non-immune-mediated. [57] Immune-mediated HIT most commonly arises five to ten days after exposure to heparin. [58] Pathogenesis of immune-mediated HIT is believed to be caused by heparin-dependent immunoglobulin antibodies binding to platelet factor 4/heparin complexes on platelets, leading to widespread platelet activation. [59]

Interactions

Foods and food supplements with blood-thinning effects include nattokinase, lumbrokinase, beer, bilberry, celery, cranberries, fish oil, garlic, ginger, ginkgo, ginseng, green tea, horse chestnut, licorice, niacin, onion, papaya, pomegranate, red clover, soybean, St. John's wort, turmeric, wheatgrass, and willow bark. [60] [61] [62] Many herbal supplements have blood-thinning properties, such as danshen and feverfew. [63] Multivitamins that do not interact with clotting are available for patients on anticoagulants. [64]

However, some foods and supplements encourage clotting. [65] These include alfalfa, avocado, cat's claw, coenzyme Q10, and dark leafy greens such as spinach. [66] [67] Excessive intake of the food mentioned above should be avoided while taking anticoagulants, or if coagulability is being monitored, their intake should be kept approximately constant so that anticoagulant dosage can be maintained at a level high enough to counteract this effect without fluctuations in coagulability. [68] [69]

Grapefruit interferes with some anticoagulant drugs, increasing the time it takes for them to be metabolized out of the body, and should be eaten with caution when on anticoagulant drugs. [70]

Anticoagulants are often used to treat acute deep-vein thrombosis. [71] [72] People using anticoagulants to treat this condition should avoid using bed rest as a complementary treatment because there are clinical benefits to continuing to walk and remaining mobile while using anticoagulants in this way. [73] Bed rest while using anticoagulants can harm patients in circumstances in which it is not medically necessary. [73]

Types

Several anticoagulants are available. Warfarin, other coumarins, and heparins have long been used. [74] Since the 2000s, several agents have been introduced that are collectively referred to as direct oral anticoagulants (DOACs), previously named novel oral anticoagulants (NOACs) or non-vitamin K antagonist oral anticoagulants. [75] [76] [77] [78] These agents include direct thrombin inhibitor (dabigatran) and factor Xa inhibitor (rivaroxaban, apixaban, betrixaban and edoxaban), and they have been shown to be as good or possibly better than the coumarins with less serious side effects. [79] The newer anticoagulants (NOACs/DOACs) are more expensive than the traditional ones and should be used in caring for patients with kidney problems. [80]

Coumarins (vitamin K antagonists)

These oral anticoagulants are derived from coumarin found in many plants. A prominent member of this class, warfarin (Coumadin), was found to be the anticoagulant most prescribed in a large multispecialty practice. [81] The anticoagulant effect takes at least 48 to 72 hours to develop. Where an immediate effect is required, heparin is given concomitantly. These anticoagulants are used to treat patients with deep-vein thrombosis (DVT) and pulmonary embolism (PE) and to prevent emboli in patients with atrial fibrillation (AF), and mechanical prosthetic heart valves. Other examples are acenocoumarol, phenprocoumon, atromentin, and phenindione.[ citation needed ]

The coumarins brodifacoum and difenacoum are used as mammalicides (particularly as rodenticides) but are not used medically.[ citation needed ]

Heparin and derivative substances

Heparin is the most widely used intravenous clinical anticoagulant worldwide. [82] Heparin is a naturally occurring glycosaminoglycan. There are three major categories of heparin: unfractionated heparin (UFH), low molecular weight heparin (LMWH), and ultra-low-molecular weight heparin (ULMWH). [83] Unfractionated heparin is usually derived from pig intestines and bovine lungs. [84] UFH binds to the enzyme inhibitor antithrombin III (AT), causing a conformational change that results in its activation. [85] The activated AT then inactivates factor Xa, thrombin, and other coagulation factors. [86] Heparin can be used in vivo (by injection), and also in vitro to prevent blood or plasma clotting in or on medical devices. In venipuncture, Vacutainer brand blood collecting tubes containing heparin usually have a green cap.[ citation needed ]

Low molecular weight heparin (LMWH)

Low molecular weight heparin (LMWH) is produced through a controlled depolymerization of unfractionated heparin. [83] LMWH exhibits a higher anti-Xa/anti-IIa activity ratio and is useful as it does not require monitoring of the APTT coagulation parameter and has fewer side effects. [83]

Synthetic pentasaccharide inhibitors of factor Xa

Direct oral

The direct oral anticoagulants (DOACs) were introduced in and after 2008. [87] There are five DOACs currently on the market: dabigatran, rivaroxaban, apixaban, edoxaban and betrixaban. [88] They were also previously referred to as "new/novel" and "non-vitamin K antagonist" oral anticoagulants (NOACs). [89]

Compared to warfarin, DOACs have a rapid onset action and relatively short half-lives; hence, they carry out their function more rapidly and effectively, allowing drugs to reduce their anticoagulation effects quickly. [90] Routine monitoring and dose adjustments of DOACs are less important than for warfarin, as they have better predictable anticoagulation activity. [91] DOAC monitoring, including laboratory monitoring and a complete medication review, should generally be conducted before initiation of a DOAC, 1–3 months after initiation, and then every 6–12 months afterwards. [92]

Both DOACs and warfarin are equivalently effective, but compared to warfarin, DOACs have fewer drug interactions, no known dietary interactions, a wider therapeutic index, and have conventional dosing that does not require dose adjustments with constant monitoring. [93] [91] However, there is no countermeasure for most DOACs, unlike for warfarin; nonetheless, the short half-lives of DOACs will allow their effects to recede swiftly. A reversal agent for dabigatran, idarucizumab, is currently available and approved for use by the FDA. Rates of adherence to DOACs are only modestly higher than adherence to warfarin among patients prescribed these drugs. Thus, adherence to anticoagulation is often poor despite hopes that DOACs would lead to higher adherence rates. [94]

DOACs are significantly more expensive than warfarin, but the patients on DOACs may experience reduced lab costs as they do not need to monitor their INR. [92]

Direct factor Xa inhibitors

Drugs such as rivaroxaban, apixaban and edoxaban work by inhibiting factor Xa directly (unlike heparins and fondaparinux, which work via antithrombin activation). Also included in this category are betrixaban from Portola Pharmaceuticals, the discontinued darexaban (YM150) from Astellas, and, more recently, the discontinued letaxaban (TAK-442) from Takeda and eribaxaban (PD0348292) from Pfizer. Betrixaban is significant as it was in 2018, the only oral factor Xa inhibitor approved by the FDA for use in acutely medically ill patients. [95] Darexaban development was discontinued in September 2011; in a trial for prevention of recurrences of myocardial infarction in addition to dual antiplatelet therapy (DAPT), the drug did not demonstrate effectiveness, and the risk of bleeding was increased by approximately 300%. [96] The development of letaxaban for acute coronary syndrome was discontinued in May 2011 following negative results from a Phase II study. [97]

Direct thrombin inhibitors

Another type of anticoagulant is the direct thrombin inhibitor. [98] Current members of this class include the bivalent drugs hirudin, lepirudin, and bivalirudin and the monovalent drugs argatroban and dabigatran. An oral direct thrombin inhibitor, ximelagatran (Exanta), was denied approval by the Food and Drug Administration (FDA) in September 2004 [99] and was pulled from the market entirely in February 2006 after reports of severe liver damage and heart attacks. [100] In November 2010, dabigatran etexilate was approved by the FDA to prevent thrombosis in atrial fibrillation.

Relevance to dental treatments

As in any invasive procedure, patients on anticoagulation therapy have an increased risk for bleeding, and caution should be used along with local hemostatic methods to minimize bleeding risk during the operation as well as postoperatively. [101] However, with regards to DOACs and invasive dental treatments, there has not been enough clinical evidence and experience to prove any reliable adverse effects, relevance or interaction between these two. [102] Further clinical prospective studies on DOACs are required to investigate the bleeding risk and hemostasis associated with surgical and dental procedures. [103]

Recommendations of modifications to the usage/dosage of DOACs before dental treatments are made based on the balance of the bleeding risk of each procedure and also the individual's own bleeding risks and renal functionality. [104] With low-bleeding-risk dental procedures, it is recommended that DOACs be continued by the patient to avoid any increase in the risk of a thromboembolic event. [105] [106] For dental procedures with a higher risk of bleeding complications (i.e. complex extractions, adjacent extractions leading to a large wound, or more than three extractions), the recommended practice is for the patient to miss or delay a dose of their DOAC before such procedures to minimize the effect on bleeding risk. [107]

Antithrombin protein therapeutics

The antithrombin protein is used as a protein therapeutic that can be purified from human plasma [108] or produced recombinantly (for example, Atryn, produced in the milk of genetically modified goats). [109] [110]

The FDA approves Antithrombin as an anticoagulant for preventing clots before, during, or after surgery or birthing in patients with hereditary antithrombin deficiency. [108] [110]

Other

Many other anticoagulants exist in research and development, diagnostics, or as drug candidates.


Reversal agents

With the growing number of patients taking oral anticoagulation therapy, studies into reversal agents are gaining increasing interest due to major bleeding events and the need for urgent anticoagulant reversal therapy. [111] Reversal agents for warfarin are more widely studied, and established guidelines for reversal exist due to a longer history of use of warfarin and the ability to get a more accurate measurement of anticoagulation effect in a patient via measuring the INR (International Normalized Ratio). [112] In general, vitamin K is most commonly used to reverse the effect of warfarin in non-urgent settings. [113] However, in urgent settings or settings with extremely high INR (INR >20), hemostatic reversal agents such as fresh frozen plasma (FFP), recombinant factor VIIa, and prothrombin complex concentrate (PCC) have been utilized with proven efficacy. [114] Specifically with warfarin, four-factor PCC (4F-PCC) has been shown to have superior safety and mortality benefits compared to FPP in lowering INR levels. [111]

Although specific antidotes and reversal agents for DOACs are not as widely studied, idarucizumab (for dabigatran) and andexanet alfa (for factor Xa inhibitor) have been used in clinical settings with varying efficacy. [89] Idarucizumab is a monoclonal antibody, approved by the US FDA in 2015, that reverses the effect of dabigatran by binding to both free and thrombin-bound dabigatran. [115] [116] Andexanet alfa is a recombinant modified human factor Xa decoy that reverses the effect of factor Xa inhibitors by binding at the active sites of factor Xa inhibitor and making it catalytically inactive. [117] [118] Andexanet alfa was approved by the US FDA in 2018. [119] Another drug called ciraparantag, a potential reversal agent for direct factor Xa inhibitors, is still under investigation. [120] Additionally, hemostatic reversal agents have also been used with varying efficacy to reverse the effects of DOACs. [121] [122]

Coagulation inhibitor measurement

A Bethesda unit (BU) is a measure of blood coagulation inhibitor activity. It is the amount of inhibitor that will inactivate half of a coagulant during the incubation period. [123] It is the standard measure used in the United States and is so named because it was adopted as a standard at a conference in Bethesda, Maryland. [124]

Laboratory use

If blood is allowed to clot, laboratory instruments, blood transfusion bags, and medical and surgical equipment will get clogged up and non-operational. In addition, test tubes used for laboratory blood tests will have chemicals added to stop blood clotting. Besides heparin, most of these chemicals bind calcium ions, preventing the coagulation proteins from using them.

Dental considerations for long-term users

Dental practitioners play an important role in the early detection of anticoagulant overdose through oral manifestations, as the patient does not show any symptoms. Dental treatment of patients taking anticoagulant or antiplatelet medication raises safety concerns in terms of the potential risk of bleeding complications following invasive dental procedures. Therefore, certain guidelines for the dental care of patients taking these drugs are needed.

Detecting overdose

An overdose of anticoagulants usually occurs in people who have heart problems and need to take anticoagulants in the long term to reduce the risk of stroke from their high blood pressure.

An International Normalised Ratio (INR) test would be recommended to confirm the overdose so that the dosage can be adjusted to an acceptable standard. The INR test measures the time it takes for a clot to form in a blood sample relative to a standard.

An INR value of 1 indicates a level of coagulation equivalent to that of an average patient not taking warfarin, and values greater than 1 indicate a longer clotting time and, thus, a longer bleeding time.

Assessing bleeding risk

There are two main parts to the assessment of bleeding risk:

Managing bleeding risk

A patient who is on anticoagulants or antiplatelet medications may undergo dental treatments which are unlikely to cause bleeding, such as local anesthesia injection, basic gum charting, removal of plaque, calculus and stain above the gum level, direct or indirect fillings which are above the gingiva, root canal treatment, taking impression for denture or crown and fitting or adjustment of orthodontic appliances.  For all these procedures, it is recommended that the dentist treat the patient following the normal standard procedure and taking care to avoid any bleeding.

For a patient who needs to undergo dental treatments which are more likely to cause bleeding, such as simple tooth extractions (1-3 teeth with small wound size), drainage of swelling inside the mouth, periodontal charting, root planing,  direct or indirect filling which extends below the gingiva, complex filling, flap raising procedure, gingival recontouring and biopsies, the dentist needs to take extra precautions apart from the standard procedure. The recommendations [126] are as follows:

There is general agreement that in most cases, treatment regimens with older anticoagulants (e.g., warfarin) and antiplatelet agents (e.g., clopidogrel, ticlopidine, prasugrel, ticagrelor, and/or aspirin) should not be altered before dental procedures. The risks of stopping or reducing these medication regimens (i.e., thromboembolism, stroke, myocardial infarction) far outweigh the consequences of prolonged bleeding, which can be controlled with local measures. In patients with other existing medical conditions that can increase the risk of prolonged bleeding after dental treatment or receiving other therapy that can increase bleeding risk, dental practitioners may wish to consult the patient's physician to determine whether care can safely be delivered in a primary care office. Any suggested modification to the medication regimen before dental surgery should be done in consultation and on the advice of the patient's physician.

Based on limited evidence, the consensus appears to be that in most patients who are receiving the newer direct-acting oral anticoagulants (i.e., dabigatran, rivaroxaban, apixaban, or edoxaban) and undergoing dental treatment (in conjunction with usual local measures to control bleeding), no change to the anticoagulant regimen is required. In patients deemed to be at higher risk of bleeding (e.g., patients with other medical conditions or undergoing more extensive procedures associated with higher bleeding risk), consideration may be given, in consultation with and on advice of the patient's physician, to postponing the timing of the daily dose of the anticoagulant until after the procedure; timing the dental intervention as late as possible after last dose of anticoagulant; or temporarily interrupting drug therapy for 24 to 48 hours.

Research

A substantial number of compounds are being investigated for use as anticoagulants. The most promising ones act on the contact activation system (factor XIIa and factor XIa); it is anticipated that this may provide agents that prevent thrombosis without conferring a risk of bleeding. [127]

As of November 2021, the direct factor XIa inhibitor milvexian is in Phase II clinical trials for the prevention of an embolism after surgery. [128]

See also

Related Research Articles

An antiplatelet drug (antiaggregant), also known as a platelet agglutination inhibitor or platelet aggregation inhibitor, is a member of a class of pharmaceuticals that decrease platelet aggregation and inhibit thrombus formation. They are effective in the arterial circulation where classical Vitamin K antagonist anticoagulants have minimal effect.

<span class="mw-page-title-main">Venous thrombosis</span> Blood clot (thrombus) that forms within a vein

Venous thrombosis is the blockage of a vein caused by a thrombus. A common form of venous thrombosis is deep vein thrombosis (DVT), when a blood clot forms in the deep veins. If a thrombus breaks off (embolizes) and flows to the lungs to lodge there, it becomes a pulmonary embolism (PE), a blood clot in the lungs. The conditions of DVT only, DVT with PE, and PE only, are all captured by the term venous thromboembolism (VTE).

<span class="mw-page-title-main">Warfarin</span> Anticoagulant medication

Warfarin is an anticoagulant used as a medication under several brand names including Coumadin. While the drug is described as a "blood thinner", it does not reduce viscosity but rather inhibits coagulation. Accordingly, it is commonly used to prevent blood clots in the circulatory system such as deep vein thrombosis and pulmonary embolism, and to protect against stroke in people who have atrial fibrillation, valvular heart disease, or artificial heart valves. Less commonly, it is used following ST-segment elevation myocardial infarction (STEMI) and orthopedic surgery. It is usually taken by mouth, but may also be administered intravenously.

<span class="mw-page-title-main">Deep vein thrombosis</span> Formation of a blood clot (thrombus) in a deep vein

Deep vein thrombosis (DVT) is a type of venous thrombosis involving the formation of a blood clot in a deep vein, most commonly in the legs or pelvis. A minority of DVTs occur in the arms. Symptoms can include pain, swelling, redness, and enlarged veins in the affected area, but some DVTs have no symptoms.

Low-molecular-weight heparin (LMWH) is a class of anticoagulant medications. They are used in the prevention of blood clots and, in the treatment of venous thromboembolism, and the treatment of myocardial infarction.

<span class="mw-page-title-main">Prothrombin time</span> Assay for evaluating the extrinsic pathway & common pathway of coagulation

The prothrombin time (PT) – along with its derived measures of prothrombin ratio (PR) and international normalized ratio (INR) – is an assay for evaluating the extrinsic pathway and common pathway of coagulation. This blood test is also called protime INR and PT/INR. 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. PT measures the following coagulation factors: I (fibrinogen), II (prothrombin), V (proaccelerin), VII (proconvertin), and X.

<span class="mw-page-title-main">Thromboembolism</span> Obstruction of a blood vessel by a clot

Thromboembolism is a condition in which a blood clot (thrombus) breaks off from its original site and travels through the bloodstream to obstruct a blood vessel, causing tissue ischemia and organ damage. Thromboembolism can affect both the venous and arterial systems, with different clinical manifestations and management strategies.

<span class="mw-page-title-main">Argatroban</span> Pharmaceutical drug

Argatroban is an anticoagulant that is a small molecule direct thrombin inhibitor. In 2000, argatroban was licensed by the Food and Drug Administration (FDA) for prophylaxis or treatment of thrombosis in patients with heparin-induced thrombocytopenia (HIT). In 2002, it was approved for use during percutaneous coronary interventions in patients who have HIT or are at risk for developing it. In 2012, it was approved by the MHRA in the UK for anticoagulation in patients with heparin-induced thrombocytopenia Type II (HIT) who require parenteral antithrombotic therapy.

<span class="mw-page-title-main">Rivaroxaban</span> Anticoagulant drug

Rivaroxaban, sold under the brand name Xarelto among others, is an anticoagulant medication used to treat and prevent blood clots. Specifically it is used to treat deep vein thrombosis and pulmonary emboli and prevent blood clots in atrial fibrillation and following hip or knee surgery. It is taken by mouth.

<span class="mw-page-title-main">Dabigatran</span> Anticoagulant medication

Dabigatran, sold under the brand name Pradaxa among others, is an anticoagulant used to treat and prevent blood clots and to prevent stroke in people with atrial fibrillation. Specifically it is used to prevent blood clots following hip or knee replacement and in those with a history of prior clots. It is used as an alternative to warfarin and does not require monitoring by blood tests. In a meta analysis of 7 different studies, there was no benefit of dabigatran over warfarin in preventing ischemic stroke; however, dabigatran were associated with a lower hazard for intracranial bleeding compared with warfarin, but also had a higher risk of gastrointestinal bleeding relative to warfarin. It is taken by mouth.

Prothrombin complex concentrate (PCC), also known as factor IX complex, sold under the brand name Kcentra among others, is a combination medication made up of blood clotting factors II, IX, and X. Some versions also contain factor VII. It is used to treat and prevent bleeding in hemophilia B if pure factor IX is not available. It may also be used for reversal of warfarin therapy. It is given by slow injection into a vein.

Direct thrombin inhibitors (DTIs) are a class of medication that act as anticoagulants by directly inhibiting the enzyme thrombin. Some are in clinical use, while others are undergoing clinical development. Several members of the class are expected to replace heparin and warfarin in various clinical scenarios.

Hypercoagulability in pregnancy is the propensity of pregnant women to develop thrombosis. Pregnancy itself is a factor of hypercoagulability, as a physiologically adaptive mechanism to prevent post partum bleeding. However, when combined with an additional underlying hypercoagulable states, the risk of thrombosis or embolism may become substantial.

Direct factor Xa inhibitors (xabans) are anticoagulants, used to both treat and prevent blood clots in veins, and prevent stroke and embolism in people with atrial fibrillation (AF).

<span class="mw-page-title-main">Vitamin K antagonist</span>

Vitamin K antagonists (VKA) are a group of substances that reduce blood clotting by reducing the action of vitamin K. The term "vitamin K antagonist" is technically a misnomer, as the drugs do not directly antagonize the action of vitamin K in the pharmacological sense, but rather the recycling of vitamin K. Vitamin K antagonists (VKAs) have been the mainstay of anticoagulation therapy for more than 50 years.

The management of atrial fibrillation (AF) is focused on preventing temporary circulatory instability, stroke and other ischemic events. Control of heart rate and rhythm are principally used to achieve the former, while anticoagulation may be employed to decrease the risk of stroke. Within the context of stroke, the discipline may be referred to as stroke prevention in atrial fibrillation (SPAF). In emergencies, when circulatory collapse is imminent due to uncontrolled rapid heart rate, immediate cardioversion may be indicated.

<span class="mw-page-title-main">Apixaban</span> Anticoagulant medication

Apixaban, sold under the brand name Eliquis, is an anticoagulant medication used to treat and prevent blood clots and to prevent stroke in people with nonvalvular atrial fibrillation through directly inhibiting factor Xa. Specifically, it is used to prevent blood clots following hip or knee replacement and in those with a history of prior clots. It is used as an alternative to warfarin and does not require monitoring by blood tests or dietary restrictions. It is taken by mouth.

<span class="mw-page-title-main">Darexaban</span> Chemical compound

Darexaban (YM150) is a direct inhibitor of factor Xa created by Astellas Pharma. It is an experimental drug that acts as an anticoagulant and antithrombotic to prevent venous thromboembolism after a major orthopaedic surgery, stroke in patients with atrial fibrillation and possibly ischemic events in acute coronary syndrome. It is used in form of the maleate. The development of darexaban was discontinued in September 2011.

Direct thrombin inhibitors (DTIs) are a class of anticoagulant drugs that can be used to prevent and treat embolisms and blood clots caused by various diseases. They inhibit thrombin, a serine protease which affects the coagulation cascade in many ways. DTIs have undergone rapid development since the 90's. With technological advances in genetic engineering the production of recombinant hirudin was made possible which opened the door to this new group of drugs. Before the use of DTIs the therapy and prophylaxis for anticoagulation had stayed the same for over 50 years with the use of heparin derivatives and warfarin which have some well known disadvantages. DTIs are still under development, but the research focus has shifted towards factor Xa inhibitors, or even dual thrombin and fXa inhibitors that have a broader mechanism of action by both inhibiting factor IIa (thrombin) and Xa. A recent review of patents and literature on thrombin inhibitors has demonstrated that the development of allosteric and multi-mechanism inhibitors might lead the way to a safer anticoagulant.

<span class="mw-page-title-main">Thrombosis prevention</span> Medical treatment

Thrombosis prevention or thromboprophylaxis is medical treatment to prevent the development of thrombosis in those considered at risk for developing thrombosis. Some people are at a higher risk for the formation of blood clots than others, such as those with cancer undergoing a surgical procedure. Prevention measures or interventions are usually begun after surgery as the associated immobility will increase a person's risk.

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