With the proper functioning of the coagulated and anticoagulated blood systems , the internal balance of the body normalizes. The blood flow through the vessels has no obstacles and restrictions, and thrombosis is at the right level. When the balance of the functioning of systems is disturbed in favor of enhancing blood coagulation, conditions appear that can lead to excessive clot formation. Indirect anticoagulants are one of the groups of drugs used to restore internal disorders.
What are anticoagulants?
Anticoagulants are drugs that have an anticoagulant effect and activate blood thinning. This allows you to restore rheological features and reduce the level of development of thrombosis.
Funds are available in tablet forms, in the form of ointments, gels and injection preparations. They are prescribed not only for the treatment of diseases, but also with the goal of preventing increased formation of blood clots.
Most representatives of this group of drugs act not on the formed blood clot, but on the activity of the coagulation system. There is a process of exposure to plasma factors and thrombin production, which slows down thrombosis.
The drugs are divided into two groups depending on their action:
- direct anticoagulants;
- indirect anticoagulants.
Direct-acting drugs based on heparin
This group of drugs has a direct effect on plasma cofactors that inhibit thrombin. The main representative is heparin. Based on it, there are a number of medicines that act similarly and have a consonant name:
- Ardeparin.
- Nadroparin.
- Klivarin.
- "Longiparin."
- "Sandoparin."
Heparin or derivatives combine with antithrombin-III, which leads to a change in the location of its molecules. This accelerates the attachment of the cofactor to thrombin, and then to the inactivation of the coagulation process.
Features of the use of "Heparin"
The action of the substance is aimed at preventing the growth and spread of a blood clot. Heparin molecules form a complex with antithrombin, which is an inhibitor of coagulation factors. The substance is a chain of glycosaminoglycans. The drug is administered subcutaneously and begins its action after a couple of hours.
If necessary, fast action "Heparin" is administered infusion intravenously in order to accelerate the effectiveness and increase bioavailability. The choice of dosage of the drug depends on the condition in which the patient is. In addition, the presence of concomitant diseases, the parallel intake of other groups of medicines, the need for surgical interventions on the vessels are taken into account.
Oligopeptides
Medications that act directly on the thrombin activation center are considered to be strong specific inhibitors of the thrombus formation system. The active substances of the drugs independently combine with coagulation factors, changing their conformation.
These are drugs "Inogatran", "Hirudin", "Efegatran", "Tromstop" and others. They are used to prevent the development of heart attacks with angina pectoris, with varicose veins, for the prevention of thromboembolism, reocclusion with vascular plastic.
Indirect anticoagulants (list)
The first anticoagulant was obtained in the 20th century in the United States, when a new disease of cows was discovered that provoked heavy bleeding. When the cause of the pathological condition was clarified, it turned out that the clover infected with the mold in the feed acts on the animal organism. From this raw material was synthesized the first drug of indirect antiplatelet effect - "Dikumarol."
To date, the list of funds, which are analogues, is more than a hundred items. All of these drugs are indirect anticoagulants. The mechanism of action of a group of medicines is based on the inhibition of the action of vitamin K.
There are coagulation factors that depend on this vitamin. Indirect anticoagulants inhibit the activation of coagulation proteins and vitamin-dependent cofactors. Uncontrolled use of such drugs is prohibited, since the risk of hemorrhagic complications increases.
There are two main groups into which all indirect anticoagulants are divided. The classification of funds is based on the active substance that is part of the drugs. Distinguish:
- coumarin derivatives;
- Indandion based products.
Indandion preparations
After conducting a large number of studies, scientists have found that it is not worth using drugs based on this active substance in therapy. The drugs had a significant amount of side effects in the form of allergic reactions. The effectiveness of the impact on the anticoagulation system also did not show stable results.
This group of medicines includes drugs: Fenindion, Diphenindion, Anisindion. It was decided to stop the main choice on the second group of antiplatelet agents, and of the derivatives of indandion at the moment only “Phenylin” is used.
The drug has a low cost, is available in tablet forms. Valid for 10 hours, and it is very important to maintain the necessary duration of therapy. The effect occurs only 24 hours after the first dose. The use of funds occurs under the monitoring of the patient's condition using laboratory blood parameters (coagulogram, general tests, biochemistry).
Scheme of application of “Phenylin”:
- The first day - 1 tablet 4 times.
- The second day - 1 tablet 3 times.
- The rest of the therapy is 1 tablet per day.
The drug is not recommended to be taken simultaneously with drugs that reduce the level of glucose in the body.
Coumarin derivatives
Coumarin is a substance that is found in plants and can be synthetically produced under laboratory conditions. At first, after its removal, the drug was used as a poison for fighting rodents. Only after the passage of time did the drug begin to be used to combat excessive thrombosis.
Indirect anticoagulants - coumarin-based drugs - are represented by the following medications:
- "Warfarin" (its analogues are "Marevan", "Warfarin sodium", "Warfarex").
- "Acenocumarol" (analogue - "Sincumar").
- "Neodicumarin" (analogue - "Ethylbiscum acetate").
Warfarin: features of application
Indirect anticoagulants (the list is in the article) are most often represented by Warfarin. This is a tablet product, available in 2.5, 3 or 5 mg. The effect on the human body develops after 1.5-3 days from the moment of the first pill intake. The maximum effect develops by the end of the first week.
After taking the drug, the rheological blood counts return to normal after 5 days from the date of withdrawal of "Warfarin". The tool is used 2 times a day at the same time. On the 5th day from the start of therapy, a blood test is performed to determine the feasibility and effectiveness of the application.
The course of treatment is selected by a specialist in each case individually. Some pathological conditions (for example, atrial fibrillation) require constant use. With the development of pulmonary embolism (pulmonary embolism), an antiplatelet agent is prescribed for at least six months or for life.
If necessary, surgery “Warfarin” must be canceled 5 days before the operation. This will allow blood counts to return to normal. With a high need to continue using anticoagulant therapy, this remedy is replaced by non-fractional heparin. The last dose is administered 4 hours before the intervention.
After surgery, after 4 hours, non-fractional heparin is reintroduced. Reception of indirect antiplatelet agents can be returned in two days, after monitoring the state of the blood using laboratory tests.
In what cases are anticoagulants prescribed?
Direct and indirect anticoagulants are used to prevent the development of thromboembolism, acute venous thrombosis, in the case of mechanical prosthetics of heart valves and the development of atrial fibrillation.
The main diseases, with the development of which anticoagulants of direct and indirect action are prescribed, have the following division into groups:
- Arterial thrombosis:
- myocardial infarction;
- pulmonary embolism;
- stroke with manifestations of ischemia;
- traumatic damage to arteries against the background of atherosclerosis.
- Disseminated intravascular coagulation :
- shock conditions;
- traumatic injuries;
- the development of sepsis.
- Acute vein thrombosis:
- thrombosis on the background of varicose veins;
- thrombosis of hemorrhoidal venous plexuses;
- clot formation in the inferior vena cava.
The main contraindications
Indirect anticoagulants are drugs that are strictly prohibited in the presence of lactose deficiency, malabsorption of glucose or galactose. There are a number of drugs that can not be used simultaneously with indirect anticoagulants. The list of drugs consists of non-steroidal anti-inflammatory drugs: Aspirin, Dipyridamole, Clopidogrel, Penicillin, Chloramphenicol, Cimetidine.
Conditions in which you can not use anticoagulants of direct and indirect action:
- gastrointestinal ulcer;
- vascular aneurysms;
- liver disease
- acute bleeding;
- thrombocytopenia;
- renal failure;
- I trimester and last month of pregnancy;
- high creatinine.
Side effects of antiplatelet agents
Each of the drugs in this group of drugs has similar side effects. They occur with self-medication, improperly selected dose or violation of recommendations for use.
Side effects include the development of bleeding, dyspeptic manifestations in the form of vomiting, nausea and diarrhea. There is severe pain in the abdomen, allergic skin rashes, such as urticaria or eczema. Necrosis, hair loss, and itching of the skin may develop.
Before starting therapy, the patient must undergo a series of tests to determine the possibility of using such drugs. The patient undergoes a general blood test, biochemistry, a general urine test, urine according to Nechiporenko, a coagulogram. It is also recommended to do an ultrasound examination of the kidneys and donate feces for occult blood.
Overdose of indirect anticoagulants
Overdose cases of this group of drugs are quite rare. This can happen if a small child finds the drug at home and tastes it. Typically, the concentration of the substance is low, so a single dose of the pill is not terrible. In the case of special or unintended use of large doses of the substance, coagulopathy and bleeding may develop.
An overdose clinic does not have specific symptoms, so it’s quite difficult to guess that a large amount of the drug was taken. Symptoms of manifestations are similar to various diseases and pathological conditions of the body. The patient appears:
- light bruises on the skin;
- the appearance of blood in urine or feces;
- uterine bleeding;
- hematomas in the neck;
- intracranial hemorrhage.
A previous stroke, old age, a history of gastrointestinal bleeding and low hematocrit are associated factors that can reduce the threshold for the susceptibility of drug concentration.
Antiaggregant Overdose Therapy
- To clean or rinse the stomach a few hours after taking the drugs does not make any sense.
- The patient is given activated charcoal for intestinal absorption.
- In case of an overdose of "Warfarin" or its analogues, "Cholestyramine" is prescribed inside.
- The patient is placed in anti-traumatic conditions to avoid the appearance of new hematomas and hemorrhages.
- With significant blood loss, transfusion of the formed elements of blood or plasma, sometimes whole blood, is carried out. Erythrocyte mass, cryoprecipitate, prothrombin complex are effective in use.
- "Fitomenadion" is prescribed, preparations based on vitamin K.
- If it is not necessary to prescribe antiplatelet therapy, then the Fitomenadion drug is prescribed as a course of treatment, and not as a first aid.
If the patient’s condition has returned to normal, but he needs to continue to use indirect anticoagulants, then he needs to temporarily replace “Warfarin” with heparin preparations.
Conclusion
The use of antiplatelet drugs allows not only to normalize the rheological standards of the blood, but also to improve the general condition of the patient and prevent the possibility of developing serious diseases.
A careful attitude to the use of anticoagulants, the choice of dosage and monitoring of the patient's condition will help reduce the risk of complications and achieve success. Specialists who use this group of drugs in their practice need to improve their knowledge and strictly follow international medical recommendations.