Misplaced Pages

#822177

95-749: An anticoagulant , commonly known as a blood thinner , is a chemical substance that prevents or reduces the coagulation of blood , prolonging the clotting time . 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. As a class of medications , anticoagulants are used in therapy for thrombotic disorders . Oral anticoagulants (OACs) are taken by many people in pill or tablet form, and various intravenous anticoagulant dosage forms are used in hospitals. Some anticoagulants are used in medical equipment, such as sample tubes, blood transfusion bags, heart–lung machines , and dialysis equipment. One of

190-452: A chemical reaction form a chemical compound . All compounds are substances, but not all substances are compounds. A chemical compound can be either atoms bonded together in molecules or crystals in which atoms, molecules or ions form a crystalline lattice . Compounds based primarily on carbon and hydrogen atoms are called organic compounds , and all others are called inorganic compounds . Compounds containing bonds between carbon and

285-660: A database and is popularly known as the Chemical substances index. Other computer-friendly systems that have been developed for substance information are: SMILES and the International Chemical Identifier or InChI. Often a pure substance needs to be isolated from a mixture , for example from a natural source (where a sample often contains numerous chemical substances) or after a chemical reaction (which often gives mixtures of chemical substances). Stoichiometry ( / ˌ s t ɔɪ k i ˈ ɒ m ɪ t r i / )

380-574: A mixture , referencing them in the chemical substances index allows CAS to offer specific guidance on standard naming of alloy compositions. Non-stoichiometric compounds are another special case from inorganic chemistry , which violate the requirement for constant composition. For these substances, it may be difficult to draw the line between a mixture and a compound, as in the case of palladium hydride . Broader definitions of chemicals or chemical substances can be found, for example: "the term 'chemical substance' means any organic or inorganic substance of

475-618: A "ligand". However, the center does not need to be a metal, as exemplified by boron trifluoride etherate BF 3 OEt 2 , where the highly Lewis acidic , but non-metallic boron center takes the role of the "metal". If the ligand bonds to the metal center with multiple atoms, the complex is called a chelate . In organic chemistry, there can be more than one chemical compound with the same composition and molecular weight. Generally, these are called isomers . Isomers usually have substantially different chemical properties, and often may be isolated without spontaneously interconverting. A common example

570-429: A DOAC, 1–3 months after initiation, and then every 6–12 months afterwards. 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. However, there is no countermeasure for most DOACs, unlike for warfarin; nonetheless,

665-524: 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. The most serious and common adverse side effects associated with anticoagulants are increased risk of bleeding, both nonmajor and major bleeding events. 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

760-416: A chemical reaction takes place and a new substance is formed, the compound iron(II) sulfide , with chemical formula FeS. The resulting compound has all the properties of a chemical substance and is not a mixture. Iron(II) sulfide has its own distinct properties such as melting point and solubility , and the two elements cannot be separated using normal mechanical processes; a magnet will be unable to recover

855-423: A conformational change that results in its activation. The activated AT then inactivates factor Xa , thrombin , and other coagulation factors. 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. Low molecular weight heparin (LMWH)

950-682: 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. The antithrombin protein is used as a protein therapeutic that can be purified from human plasma or produced recombinantly (for example, Atryn, produced in the milk of genetically modified goats). The FDA approves Antithrombin as an anticoagulant for preventing clots before, during, or after surgery or birthing in patients with hereditary antithrombin deficiency. Many other anticoagulants exist in research and development , diagnostics , or as drug candidates. With

1045-423: A larger histologic scale, pseudopalisades (false palisades ) are hypercellular zones that typically surround necrotic tissue. Pseudopalisading necrosis indicates an aggressive tumor. There are many causes of necrosis, and as such treatment is based upon how the necrosis came about. Treatment of necrosis typically involves two distinct processes: Usually, the underlying cause of the necrosis must be treated before

SECTION 10

#1732858782823

1140-471: A life-threatening bleeding rate of 1-3% per year. Newer non-vitamin K antagonist oral anticoagulants appear to have fewer life-threatening bleeding events than warfarin. Additionally, patients aged 80 years or more may be especially susceptible to bleeding complications, with a rate of 13 bleeds per 100 person-years. Bleeding risk is especially important to consider in patients with renal impairment and NOAC therapy because all NOACs, to some extent, are excreted by

1235-436: A metal are called organometallic compounds . Compounds in which components share electrons are known as covalent compounds. Compounds consisting of oppositely charged ions are known as ionic compounds, or salts . Coordination complexes are compounds where a dative bond keeps the substance together without a covalent or ionic bond. Coordination complexes are distinct substances with distinct properties different from

1330-676: A part of an organ which results in failure of nutrition); injury and paralysis of nerve cells. Pancreatic enzymes (lipases) are the major cause of fat necrosis. Necrosis can be activated by components of the immune system, such as the complement system ; bacterial toxins ; activated natural killer cells ; and peritoneal macrophages . Pathogen-induced necrosis programs in cells with immunological barriers ( intestinal mucosa ) may alleviate invasion of pathogens through surfaces affected by inflammation. Toxins and pathogens may cause necrosis; toxins such as snake venoms may inhibit enzymes and cause cell death. Necrotic wounds have also resulted from

1425-462: A particular molecular identity, including – (i) any combination of such substances occurring in whole or in part as a result of a chemical reaction or occurring in nature". In the field of geology , inorganic solid substances of uniform composition are known as minerals . When two or more minerals are combined to form mixtures (or aggregates ), they are defined as rocks . Many minerals, however, mutually dissolve into solid solutions , such that

1520-857: A patient via measuring the INR (International Normalized Ratio). In general, vitamin K is most commonly used to reverse the effect of warfarin in non-urgent settings. 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. 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. 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. Idarucizumab

1615-426: A potential reversal agent for direct factor Xa inhibitors, is still under investigation. Additionally, hemostatic reversal agents have also been used with varying efficacy to reverse the effects of DOACs. 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. It is the standard measure used in

1710-464: 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. Routine monitoring and dose adjustments of DOACs are less important than for warfarin, as they have better predictable anticoagulation activity. DOAC monitoring, including laboratory monitoring and a complete medication review, should generally be conducted before initiation of

1805-500: A risk of bleeding. Generally, the benefit of anticoagulation is preventing or reducing the progression of a thromboembolic disease. 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. 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

1900-437: A separate chemical substance. However, the polymer may be defined by a known precursor or reaction(s) and the molar mass distribution . For example, polyethylene is a mixture of very long chains of -CH 2 - repeating units, and is generally sold in several molar mass distributions, LDPE , MDPE , HDPE and UHMWPE . The concept of a "chemical substance" became firmly established in the late eighteenth century after work by

1995-400: A simple mixture. Typically these have a metal, such as a copper ion, in the center and a nonmetals atom, such as the nitrogen in an ammonia molecule or oxygen in water in a water molecule, forms a dative bond to the metal center, e.g. tetraamminecopper(II) sulfate [Cu(NH 3 ) 4 ]SO 4 ·H 2 O. The metal is known as a "metal center" and the substance that coordinates to the center is called

SECTION 20

#1732858782823

2090-479: A single chemical substance ( allotropes ). For instance, oxygen exists as both diatomic oxygen (O 2 ) and ozone (O 3 ). The majority of elements are classified as metals . These are elements with a characteristic lustre such as iron , copper , and gold . Metals typically conduct electricity and heat well, and they are malleable and ductile . Around 14 to 21 elements, such as carbon , nitrogen , and oxygen , are classified as non-metals . Non-metals lack

2185-430: A single manufacturing process. For example, charcoal is an extremely complex, partially polymeric mixture that can be defined by its manufacturing process. Therefore, although the exact chemical identity is unknown, identification can be made with a sufficient accuracy. The CAS index also includes mixtures. Polymers almost always appear as mixtures of molecules of multiple molar masses, each of which could be considered

2280-723: A single rock is a uniform substance despite being a mixture in stoichiometric terms. Feldspars are a common example: anorthoclase is an alkali aluminum silicate, where the alkali metal is interchangeably either sodium or potassium. In law, "chemical substances" may include both pure substances and mixtures with a defined composition or manufacturing process. For example, the EU regulation REACH defines "monoconstituent substances", "multiconstituent substances" and "substances of unknown or variable composition". The latter two consist of multiple chemical substances; however, their identity can be established either by direct chemical analysis or reference to

2375-495: A technical specification instead of particular chemical substances. For example, gasoline is not a single chemical compound or even a particular mixture: different gasolines can have very different chemical compositions, as "gasoline" is primarily defined through source, properties and octane rating . Every chemical substance has one or more systematic names , usually named according to the IUPAC rules for naming . An alternative system

2470-442: A yellow-grey mixture. No chemical process occurs, and the material can be identified as a mixture by the fact that the sulfur and the iron can be separated by a mechanical process, such as using a magnet to attract the iron away from the sulfur. In contrast, if iron and sulfur are heated together in a certain ratio (1 atom of iron for each atom of sulfur, or by weight, 56 grams (1 mol ) of iron to 32 grams (1 mol) of sulfur),

2565-436: Is glucose vs. fructose . The former is an aldehyde , the latter is a ketone . Their interconversion requires either enzymatic or acid-base catalysis . However, tautomers are an exception: the isomerization occurs spontaneously in ordinary conditions, such that a pure substance cannot be isolated into its tautomers, even if these can be identified spectroscopically or even isolated in special conditions. A common example

2660-704: Is glucose , which has open-chain and ring forms. One cannot manufacture pure open-chain glucose because glucose spontaneously cyclizes to the hemiacetal form. All matter consists of various elements and chemical compounds, but these are often intimately mixed together. Mixtures contain more than one chemical substance, and they do not have a fixed composition. Butter , soil and wood are common examples of mixtures. Sometimes, mixtures can be separated into their component substances by mechanical processes, such as chromatography , distillation , or evaporation . Grey iron metal and yellow sulfur are both chemical elements, and they can be mixed together in any ratio to form

2755-592: Is a chemical substance made up of a particular kind of atom and hence cannot be broken down or transformed by a chemical reaction into a different element, though it can be transmuted into another element through a nuclear reaction . This is because all of the atoms in a sample of an element have the same number of protons , though they may be different isotopes , with differing numbers of neutrons . As of 2019, there are 118 known elements, about 80 of which are stable – that is, they do not change by radioactive decay into other elements. Some elements can occur as more than

2850-408: Is a form of cell injury which results in the premature death of cells in living tissue by autolysis . The term "necrosis" came about in the mid-19th century and is commonly attributed to German pathologist Rudolf Virchow , who is often regarded as one of the founders of modern pathology. Necrosis is caused by factors external to the cell or tissue, such as infection, or trauma which result in

2945-489: 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. 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. Andexanet alfa was approved by the US FDA in 2018. Another drug called ciraparantag,

Anticoagulant - Misplaced Pages Continue

3040-460: Is also a component of some physiological process. Activation-induced death of primary T lymphocytes and other important constituents of the immune response are caspase -independent and necrotic by morphology; hence, current researchers have demonstrated that necrotic cell death can occur not only during pathological processes, but also during normal processes such as tissue renewal, embryogenesis , and immune response. Until recently, necrosis

3135-402: Is an example of complete combustion . Stoichiometry measures these quantitative relationships, and is used to determine the amount of products and reactants that are produced or needed in a given reaction. Describing the quantitative relationships among substances as they participate in chemical reactions is known as reaction stoichiometry . In the example above, reaction stoichiometry measures

3230-417: Is an example of a chemical substance, with a constant composition of two hydrogen atoms bonded to a single oxygen atom (i.e. H 2 O). The atomic ratio of hydrogen to oxygen is always 2:1 in every molecule of water. Pure water will tend to boil near 100 °C (212 °F), an example of one of the characteristic properties that define it. Other notable chemical substances include diamond (a form of

3325-917: Is believed to be caused by heparin-dependent immunoglobulin antibodies binding to platelet factor 4/heparin complexes on platelets, leading to widespread platelet activation. 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. Many herbal supplements have blood-thinning properties, such as danshen and feverfew . Multivitamins that do not interact with clotting are available for patients on anticoagulants. However, some foods and supplements encourage clotting. These include alfalfa , avocado , cat's claw , coenzyme Q10 , and dark leafy greens such as spinach . Excessive intake of

3420-571: Is not medically necessary. Several anticoagulants are available. Warfarin, other coumarins, and heparins have long been used. 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 . 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

3515-443: 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

3610-575: Is present. 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. Long-term warfarin and heparin usage have also been linked to osteoporosis. Another potentially severe complication associated with heparin use is called heparin-induced thrombocytopenia (HIT). There are two distinct types: HIT 1) immune-mediated and 2) non-immune-mediated. Immune-mediated HIT most commonly arises five to ten days after exposure to heparin. Pathogenesis of immune-mediated HIT

3705-631: Is produced through a controlled depolymerization of unfractionated heparin. 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. The direct oral anticoagulants (DOACs) were introduced in and after 2008. There are five DOACs currently on the market: dabigatran , rivaroxaban , apixaban , edoxaban and betrixaban . They were also previously referred to as "new/novel" and "non-vitamin K antagonist" oral anticoagulants (NOACs). Compared to warfarin, DOACs have

3800-422: 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

3895-496: 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 . The coumarins brodifacoum and difenacoum are used as mammalicides (particularly as rodenticides ) but are not used medically. Heparin

Anticoagulant - Misplaced Pages Continue

3990-480: Is the most widely used intravenous clinical anticoagulant worldwide. 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). Unfractionated heparin is usually derived from pig intestines and bovine lungs. UFH binds to the enzyme inhibitor antithrombin III (AT), causing

4085-411: Is the relationships among the weights of reactants and products before, during, and following chemical reactions . Stoichiometry is founded on the law of conservation of mass where the total mass of the reactants equals the total mass of the products, leading to the insight that the relations among quantities of reactants and products typically form a ratio of positive integers. This means that if

4180-486: Is used by the Chemical Abstracts Service (CAS). Many compounds are also known by their more common, simpler names, many of which predate the systematic name. For example, the long-known sugar glucose is now systematically named 6-(hydroxymethyl)oxane-2,3,4,5-tetrol. Natural products and pharmaceuticals are also given simpler names, for example the mild pain-killer Naproxen is the more common name for

4275-555: The United States and is so named because it was adopted as a standard at a conference in Bethesda, Maryland . 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

4370-532: The amounts of the separate reactants are known, then the amount of the product can be calculated. Conversely, if one reactant has a known quantity and the quantity of the products can be empirically determined, then the amount of the other reactants can also be calculated. This is illustrated in the image here, where the balanced equation is: Here, one molecule of methane reacts with two molecules of oxygen gas to yield one molecule of carbon dioxide and two molecules of water . This particular chemical equation

4465-404: 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

4560-498: The application, but higher tolerance of impurities is usually expected in the production of bulk chemicals. Thus, the user of the chemical in the US might choose between the bulk or "technical grade" with higher amounts of impurities or a much purer "pharmaceutical grade" (labeled "USP", United States Pharmacopeia ). "Chemicals" in the commercial and legal sense may also include mixtures of highly variable composition, as they are products made to

4655-556: The body which causes cellular breakdown), electric shock, damage to blood vessels (which may disrupt blood supply to associated tissue), and ischemia . Thermal effects (extremely high or low temperature) can often result in necrosis due to the disruption of cells, especially in bone cells. Necrosis can also result from chemical trauma, with alkaline and acidic compounds causing liquefactive and coagulative necrosis, respectively, in affected tissues. The severity of such cases varies significantly based on multiple factors, including

4750-455: The body, and should be eaten with caution when on anticoagulant drugs. Anticoagulants are often used to treat acute deep-vein thrombosis . 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. Bed rest while using anticoagulants can harm patients in circumstances in which it

4845-568: The cell walls cannot be bonded and thus an impediment of the meristems. This will lead to necrosis of stem and root tips and leaf edges. For example, necrosis of tissue can occur in Arabidopsis thaliana due to plant pathogens. Cacti such as the Saguaro and Cardon in the Sonoran Desert experience necrotic patch formation regularly; a species of Dipterans called Drosophila mettleri has developed

SECTION 50

#1732858782823

4940-408: The chemical combination of the known chemical elements. As of Feb 2021, about "177 million organic and inorganic substances" (including 68 million defined-sequence biopolymers) are in the scientific literature and registered in public databases. The names of many of these compounds are often nontrivial and hence not very easy to remember or cite accurately. Also, it is difficult to keep track of them in

5035-451: The chemical compound (S)-6-methoxy-α-methyl-2-naphthaleneacetic acid. Chemists frequently refer to chemical compounds using chemical formulae or molecular structure of the compound. There has been a phenomenal growth in the number of chemical compounds being synthesized (or isolated), and then reported in the scientific literature by professional chemists around the world. An enormous number of chemical compounds are possible through

5130-460: The chemical industry, manufactured "chemicals" are chemical substances, which can be classified by production volume into bulk chemicals, fine chemicals and chemicals found in research only: The cause of the difference in production volume is the complexity of the molecular structure of the chemical. Bulk chemicals are usually much less complex. While fine chemicals may be more complex, many of them are simple enough to be sold as "building blocks" in

5225-402: The chemical substances of which fruits and vegetables, for example, are naturally composed even when growing wild are not called "chemicals" in general usage. In countries that require a list of ingredients in products, the "chemicals" listed are industrially produced "chemical substances". The word "chemical" is also often used to refer to addictive, narcotic, or mind-altering drugs. Within

5320-419: The chemist Joseph Proust on the composition of some pure chemical compounds such as basic copper carbonate . He deduced that, "All samples of a compound have the same composition; that is, all samples have the same proportions, by mass, of the elements present in the compound." This is now known as the law of constant composition . Later with the advancement of methods for chemical synthesis particularly in

5415-437: The coagulation proteins from using them. 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

5510-449: The compound concentration, type of tissue affected, and the extent of chemical exposure. In frostbite , crystals form, increasing the pressure of remaining tissue and fluid causing the cells to burst. Under extreme conditions tissues and cells may die through an unregulated process of membrane and cytosol destruction. Internal factors causing necrosis include: trophoneurotic disorders (diseases that occur due to defective nerve action in

5605-438: 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

5700-507: The coumarins with less serious side effects. The newer anticoagulants (NOACs/DOACs) are more expensive than the traditional ones and should be used in caring for patients with kidney problems. 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. The anticoagulant effect takes at least 48 to 72 hours to develop. Where an immediate effect

5795-450: The cytoplasm, which is referred to as karyolysis . The second pathway is a secondary form of necrosis that is shown to occur after apoptosis and budding. In these cellular changes of necrosis, the nucleus breaks into fragments (known as karyorrhexis ). The nucleus changes in necrosis and characteristics of this change are determined by the manner in which its DNA breaks down: Other typical cellular changes in necrosis include: On

SECTION 60

#1732858782823

5890-430: The dead tissue itself can be dealt with. Even after the initial cause of the necrosis has been halted, the necrotic tissue will remain in the body. The body's immune response to apoptosis, which involves the automatic breaking down and recycling of cellular material, is not triggered by necrotic cell death due to the apoptotic pathway being disabled. If calcium is deficient, pectin cannot be synthesized, and therefore

5985-454: 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

6080-645: The dental intervention as late as possible after last dose of anticoagulant; or temporarily interrupting drug therapy for 24 to 48 hours. Chemical substance Chemical substances can exist in several different physical states or phases (e.g. solids , liquids , gases , or plasma ) without changing their chemical composition. Substances transition between these phases of matter in response to changes in temperature or pressure . Some chemical substances can be combined or converted into new substances by means of chemical reactions . Chemicals that do not possess this ability are said to be inert . Pure water

6175-505: 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. Darexaban development was discontinued in September 2011; in a trial for prevention of recurrences of myocardial infarction in addition to dual antiplatelet therapy (DAPT),

6270-458: The drug did not demonstrate effectiveness, and the risk of bleeding was increased by approximately 300%. The development of letaxaban for acute coronary syndrome was discontinued in May 2011 following negative results from a Phase II study. Another type of anticoagulant is the direct thrombin inhibitor . Current members of this class include the bivalent drugs hirudin , lepirudin , and bivalirudin and

6365-531: The element carbon ), table salt (NaCl; an ionic compound ), and refined sugar (C 12 H 22 O 11 ; an organic compound ). In addition to the generic definition offered above, there are several niche fields where the term "chemical substance" may take alternate usages that are widely accepted, some of which are outlined in the sections below. Chemical Abstracts Service (CAS) lists several alloys of uncertain composition within their chemical substance index. While an alloy could be more closely defined as

6460-405: The first anticoagulants, warfarin , was initially approved as a rodenticide . Anticoagulants are closely related to antiplatelet drugs and thrombolytic drugs by manipulating the various pathways of blood coagulation. Specifically, antiplatelet drugs inhibit platelet aggregation (clumping together), whereas anticoagulants inhibit specific pathways of the coagulation cascade, which happens after

6555-417: 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. Grapefruit interferes with some anticoagulant drugs, increasing the time it takes for them to be metabolized out of

6650-601: 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 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

6745-436: 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. 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

6840-713: The healing process. Thus, untreated necrosis results in a build-up of decomposing dead tissue and cell debris at or near the site of the cell death. A classic example is gangrene . For this reason, it is often necessary to remove necrotic tissue surgically , a procedure known as debridement . Structural signs that indicate irreversible cell injury and the progression of necrosis include dense clumping and progressive disruption of genetic material, and disruption to membranes of cells and organelles . There are six distinctive morphological patterns of necrosis: Necrosis may occur due to external or internal factors. External factors may involve mechanical trauma (physical damage to

6935-398: The idea of stereoisomerism – that atoms have rigid three-dimensional structure and can thus form isomers that differ only in their three-dimensional arrangement – was another crucial step in understanding the concept of distinct chemical substances. For example, tartaric acid has three distinct isomers, a pair of diastereomers with one diastereomer forming two enantiomers . An element

7030-510: The initial platelet aggregation but before the formation of fibrin and stable aggregated platelet products. Common anticoagulants include warfarin and heparin . The use of anticoagulants is a decision based on the risks and benefits of anticoagulation. The biggest risk of anticoagulation therapy is the increased risk of bleeding. 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

7125-414: The iron, since there is no metallic iron present in the compound. While the term chemical substance is a precise technical term that is synonymous with chemical for chemists, the word chemical is used in general usage to refer to both (pure) chemical substances and mixtures (often called compounds ), and especially when produced or purified in a laboratory or an industrial process. In other words,

7220-811: The kidneys. Thus, patients with renal impairment may be at higher risk of increased bleeding. In people with cancer, a systematic review has found warfarin had no effect on death rate or the risk of blood clots. 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. 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. Nonhemorrhagic adverse events are less common than hemorrhagic adverse events but should still be monitored closely. Nonhemorrhagic adverse events of warfarin include skin necrosis , limb gangrene, and purple toe syndrome. Skin necrosis and limb gangrene are most commonly observed on

7315-425: The large number of chemical substances reported in chemistry literature need to be indexed. Isomerism caused much consternation to early researchers, since isomers have exactly the same composition, but differ in configuration (arrangement) of the atoms. For example, there was much speculation about the chemical identity of benzene , until the correct structure was described by Friedrich August Kekulé . Likewise,

7410-409: The literature. Several international organizations like IUPAC and CAS have initiated steps to make such tasks easier. CAS provides the abstracting services of the chemical literature, and provides a numerical identifier, known as CAS registry number to each chemical substance that has been reported in the chemical literature (such as chemistry journals and patents ). This information is compiled as

7505-453: The loss of cell membrane integrity and an uncontrolled release of products of cell death into the extracellular space . This initiates an inflammatory response in the surrounding tissue, which attracts leukocytes and nearby phagocytes which eliminate the dead cells by phagocytosis . However, microbial damaging substances released by leukocytes would create collateral damage to surrounding tissues. This excess collateral damage inhibits

7600-426: 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

7695-411: The metallic properties described above, they also have a high electronegativity and a tendency to form negative ions . Certain elements such as silicon sometimes resemble metals and sometimes resemble non-metals, and are known as metalloids . A chemical compound is a chemical substance that is composed of a particular set of atoms or ions . Two or more elements combined into one substance through

7790-719: 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 and was pulled from the market entirely in February 2006 after reports of severe liver damage and heart attacks. In November 2010, dabigatran etexilate was approved by the FDA to prevent thrombosis in atrial fibrillation . 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

7885-439: The operation as well as postoperatively. 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. Further clinical prospective studies on DOACs are required to investigate the bleeding risk and hemostasis associated with surgical and dental procedures. Recommendations of modifications to

7980-417: The patients on DOACs may experience reduced lab costs as they do not need to monitor their INR. 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,

8075-421: The potential for bleeding while on blood thinning agents. Among these tools are HAS-BLED , ATRIA, HEMORR2HAGES, and CHA2DS2-VASc . 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. There is no evidence to indicate that adding anticoagulant therapy to standard treatment has

8170-410: The realm of organic chemistry ; the discovery of many more chemical elements and new techniques in the realm of analytical chemistry used for isolation and purification of elements and compounds from chemicals that led to the establishment of modern chemistry , the concept was defined as is found in most chemistry textbooks. However, there are some controversies regarding this definition mainly because

8265-474: The relationship between the quantities of methane and oxygen that react to form carbon dioxide and water. Because of the well known relationship of moles to atomic weights , the ratios that are arrived at by stoichiometry can be used to determine quantities by weight in a reaction described by a balanced equation. This is called composition stoichiometry . Necrosis Necrosis (from Ancient Greek νέκρωσις ( nékrōsis )  'death')

8360-469: 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. DOACs are significantly more expensive than warfarin, but

8455-640: The stings of Vespa mandarinia . Pathological conditions are characterized by inadequate secretion of cytokines . Nitric oxide (NO) and reactive oxygen species (ROS) are also accompanied by intense necrotic death of cells. A classic example of a necrotic condition is ischemia which leads to a drastic depletion of oxygen , glucose , and other trophic factors and induces massive necrotic death of endothelial cells and non-proliferating cells of surrounding tissues (neurons, cardiomyocytes, renal cells, etc.). Recent cytological data indicates that necrotic death occurs not only during pathological events but it

8550-454: The synthesis of more complex molecules targeted for single use, as named above. The production of a chemical includes not only its synthesis but also its purification to eliminate by-products and impurities involved in the synthesis. The last step in production should be the analysis of batch lots of chemicals in order to identify and quantify the percentages of impurities for the buyer of the chemicals. The required purity and analysis depends on

8645-603: The third to eighth day of therapy. 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. Purple toe syndrome typically develops three to eight weeks after initiation of warfarin therapy. 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

8740-428: 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

8835-417: The unregulated digestion of cell components. In contrast, apoptosis is a naturally occurring programmed and targeted cause of cellular death. While apoptosis often provides beneficial effects to the organism, necrosis is almost always detrimental and can be fatal. Cellular death due to necrosis does not follow the apoptotic signal transduction pathway, but rather various receptors are activated and result in

8930-475: 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. 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. For dental procedures with a higher risk of bleeding complications (i.e. complex extractions, adjacent extractions leading to

9025-410: Was thought to be an unregulated process. However, there are two broad pathways in which necrosis may occur in an organism. The first of these two pathways initially involves oncosis , where swelling of the cells occurs. Affected cells then proceed to blebbing , and this is followed by pyknosis , in which nuclear shrinkage transpires. In the final step of this pathway cell nuclei are dissolved into

#822177