With the proper functioning of the coagulated and anti-coagulable blood systems, the internal balance of the body is normalized. The blood flow through the vessels has no obstacles and restrictions, and thrombus formation is at the correct level. When the balance of functioning of the systems is disturbed in favor of increased blood clotting, conditions arise that can lead to excessive clotting. 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 development of thrombosis.
Means are available in tablet forms, in the form of ointments, gels and injectables. They are prescribed not only for the treatment of diseases, but also for the prevention of increased formation of bloodbunches.
Most of the representatives of this group of drugs do not act on the formed thrombus, but on the activity of the coagulation system. There is a process of influencing plasma factors and thrombin production, which slows down thrombus formation.
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 arrangement of its molecules. This speeds up the attachment of the cofactor to thrombin and then to the inactivation of the clotting 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 injected subcutaneously and begins its action in a couple of hours.
If you need a quick action "Heparin" injectedby intravenous infusion to accelerate effectiveness and increase bioavailability. The choice of dosage of the drug depends on the condition in which the patient is located. 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
Drugs that act directly on the thrombin activation center are considered strong specific inhibitors of the thrombus formation system. The active substances of the drugs bind themselves to clotting factors, changing their conformation.
These are Inogatran, Hirudin, Efegatran, Tromstop and others. They are used to prevent the development of heart attacks in angina pectoris, in varicose veins, to prevent thromboembolism, reocclusion in vascular plasty.
Indirect anticoagulants (list)
The first anticoagulant was obtained in the 20th century in the USA, when a new disease of cows was discovered that provokes heavy bleeding. When the cause of the pathological condition was clarified, it turned out that the organism of animals was affected by mold-infected clover found in the feed. From this raw material, the first indirect antiplatelet drug, Dicumarol, was synthesized.
To date, the list of funds that are analogues is more than a hundred items. All of these drugs are indirect anticoagulants. The mechanism of action of a group of drugs is based on the inhibition of the action of vitamin K.
There are clotting factors that depend on this vitamin. Indirect anticoagulants prevent the activation of coagulation proteins and vitamin-dependent cofactors. Uncontrolled use of such drugs is prohibited, as 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 preparations. Distinguish:
- coumarin derivatives;
- Indandion based products.
Indandione preparations
After a large number of studies, scientists have found that funds based on this active substance should not be used in therapy. The drugs had a significant number 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: Fenindione, Difenindione, Anisindione. It was decided to stop the main choice on the second group of antiplatelet agents, and of the indandione derivatives, only Phenylin is currently used.
The drug has a low cost, is available in tablet form. It acts for 10 hours, and it is very important to maintain the required duration of therapy. The effect occurs only after 24 hours from the time of the first dose. The use of funds takes place under the monitoring of the patient's condition using laboratory blood parameters (coagulogram, general tests, biochemistry).
Scheme of application of "Phenilin":
- First day - 1 eachtablet 4 times.
- Second day - 1 tablet 3 times.
- The rest of the therapy - 1 tablet per day.
The product 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 produced synthetically in the laboratory. At first, after its removal, the agent was used as a poison to control rodents. Only over time, the drug began to be used to combat excessive thrombosis.
Indirect anticoagulants - drugs based on coumarin - are represented by the following medications:
- Warfarin (its analogues are Marevan, Warfarin Sodium, Warfarex).
- "Acenocoumarol" (analogue - "Sinkumar").
- "Neocoumarin" (analogue - "Ethylbiscumacetate").
"Warfarin": application features
Indirect anticoagulants (the list is in the article) are most often represented by "Warfarin". This tablet is available in 2, 5, 3 or 5 mg. The effect on the human body develops after 1.5-3 days from the moment the first pill is taken. The maximum effect develops by the end of the first week.
After the end of taking the drug, the rheological parameters of the blood return to normal after 5 days from the day the "Warfarin" was canceled. The remedy is applied 2 times a day at the same time. On the 5th day from the start of therapyconduct a blood test to determine the appropriateness 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 PE (pulmonary embolism), an antiplatelet agent is prescribed for at least six months or for life.
If surgery is required, Warfarin should be canceled 5 days before surgery. This will allow the blood counts to return to normal. If there is a high need to continue the use of anticoagulant therapy, this agent is replaced by non-fractional heparin. The last dose is administered 4 hours before the intervention.
After the operation, non-fractional heparin is reintroduced 4 hours later. Reception of indirect antiplatelet agents can be returned after two days, after monitoring the state of the blood using laboratory tests.
When are anticoagulants prescribed?
Direct and indirect anticoagulants are used to prevent the development of thromboembolism, acute thrombosis of the venous system, in the case of mechanical prosthetic heart valves and the development of atrial fibrillation.
The main diseases, in the development of which anticoagulants of direct and indirect action are prescribed, have the following division into groups:
-
Thrombosis of the arterial system:
- myocardial infarction;
- pulmonary embolism;
- stroke with manifestationsischemia;
- traumatic damage to the arteries due to atherosclerosis.
-
Disseminated intravascular coagulation:
- shock states;
- traumatic injury;
- development of sepsis.
-
Acute vein thrombosis:
- thrombosis against the background of varicose veins;
- thrombosis of hemorrhoidal venous plexuses;
- Clot formation in the inferior vena cava.
Main contraindications
Indirect anticoagulants are drugs that are strictly prohibited in the presence of lactose deficiency, glucose or galactose malabsorption. 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 direct and indirect anticoagulants cannot be used:
- ulcerative diseases of the gastrointestinal tract;
- vascular aneurysms;
- liver disease;
- acute bleeding;
- thrombocytopenia;
- kidney failure;
- I trimester and last month of pregnancy;
- high creatinine.
Side effects of antiplatelet drugs
Each of the drugs in this group of drugs has similar side effects. They appear with self-medication, the wrong dose, or violation of recommendations for use.
Kside 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 like urticaria or eczema. Necrosis, hair loss, skin itching may develop.
Before starting therapy, the patient must pass a series of tests to determine the possibility of using such drugs. The patient takes a general blood test, biochemistry, a general urinalysis, 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. Usually the concentration of the substance is low, so a single dose of the pill is not terrible. In case of special or unintentional use of large doses of the substance, coagulopathy and bleeding may develop.
The overdose clinic has no specific symptoms, so it is quite difficult to guess that a large amount of the drug has been taken. Symptoms of manifestations are similar to various diseases and pathological conditions of the body. The patient appears:
- light bruising on the skin;
- blood in urine or feces;
- uterine bleeding;
- hematomas in the neck;
- intracranial hemorrhage.
Previous stroke, advanced age, history of gastrointestinal bleeding and low hematocrit are concomitant factors that may decrease drug exposure thresholds.
Antiplatelet overdose therapy
- There is no point in emptying or rinsing the stomach a few hours after taking the drugs.
- The patient is given activated charcoal for intestinal absorption.
- In case of an overdose of "Warfarin" or its analogues, "Cholestyramine" is prescribed orally.
- The patient is placed in anti-traumatic conditions to avoid the appearance of new hematomas and hemorrhages.
- With significant blood loss, a transfusion of blood cells or plasma, sometimes whole blood, is carried out. Erythrocyte mass, cryoprecipitate, prothrombin complex are effective in use.
- Fitomenadione is prescribed, preparations based on vitamin K.
- If there is no need to prescribe antiplatelet therapy, then Fitomenadione is prescribed as a course of treatment, and not as first aid.
If the patient's condition has returned to normal, but he needs to continue using indirect anticoagulants, then you need to temporarily replace Warfarin with heparin drugs.
Conclusion
The use of antiplatelet drugs allows not only to normalize blood rheological standards, but also to improve the general condition of the patient andprevent the possibility of developing serious diseases.
Careful attention to the use of anticoagulants, dosage selection 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.
