Warfarin - instructions for use, reviews, analogs and formulations (tablets 2.5 mg) of the drug for the treatment and prevention of thrombosis and embolism of blood vessels in adults, children and pregnancy. Interaction with alcohol and diet

In this article, you can read the instructions for using the drug Warfarin. There are reviews of visitors to the site - consumers of this medication, as well as opinions of doctors of specialists on the use of Warfarin in their practice. A big request is to actively add their feedback on the drug: the medicine helped or did not help get rid of the disease, which were observed complications and side effects, possibly not declared by the manufacturer in the annotation. Warfarin analogs in the presence of existing structural analogs.Use for the treatment and prevention of thrombosis and embolism of vessels of adults, children, as well as during pregnancy and lactation. Interaction of the drug with alcohol.

Warfarin - an anticoagulant of indirect action. It blocks in the liver the synthesis of vitamin K-dependent clotting factors, namely, 2, 7, 9 and 10. The concentration of these components in the blood decreases, the process of blood clotting slows down.

The onset of anticoagulant action is observed 36-72 hours after the beginning of application of the drug with the development of maximum effect on 5-7 days from the beginning of application. After discontinuation of the drug, the restoration of vitamin K-dependent coagulation factors occurs within 4-5 days.

Composition

Warfarin sodium + excipients.

Pharmacokinetics

Warfarin is rapidly absorbed from the digestive tract. Metabolised in the liver. Warfarin is excreted from the body in the form of inactive metabolites with bile, which are reabsorbed into the digestive tract and excreted in the urine.

Indications

Treatment and prevention of thrombosis and embolism of blood vessels:

• acute venous thrombosis and pulmonary embolism;
• postoperative thrombosis;
• repeated myocardial infarction;
• as an additional tool for surgical or medicamentous (thrombolytic) treatment of thrombosis, as well as for electrical cardioversion of atrial fibrillation;
• recurrent venous thrombosis;
• repeated embolism of the pulmonary artery;
• Prosthesis of valvular and vascular valves (combination with acetylsalicylic acid is possible);
• thrombosis of peripheral, coronary and cerebral arteries;
• secondary prevention of thrombosis and thromboembolism after myocardial infarction and atrial fibrillation;
• treatment and prevention of transient ischemic attacks and strokes.

Forms of release

Tablets 2.5 mg.

Instructions for use and dosage

Warfarin is prescribed once a day at the same time. The duration of treatment is determined by the doctor in accordance with the indications for use.

Before the start of therapy, MHO is determined. Further laboratory monitoring is carried out regularly every 4-8 weeks.

The duration of treatment depends on the clinical condition of the patient; treatment can be canceled immediately.

The initial dose for patients who had not previously used warfarin was 5 mg per day (2 tablets) for the first 4 days.On the 5th day of treatment, MHO is determined and, according to this indicator, a maintenance dose of the drug is administered. Usually the maintenance dose of the drug is 2.5-7.5 mg per day (1-3 tablets).

For patients who previously used warfarin, the recommended starting dose is a double dose of a known maintenance dose of the drug and is administered within the first 2 days. The treatment is then continued with a known maintenance dose. On the 5th day of treatment, MHO monitoring and dose adjustment are performed in accordance with this indicator.

It is recommended to maintain the MHO index from 2 to 3 in case of prophylaxis and treatment of venous thrombosis, pulmonary embolism, atrial fibrillation, dilated cardiomyopathy, complicated heart valve diseases, prosthesis of the heart valves with bioprostheses. Higher MHO values ​​from 2.5 to 3.5 are recommended for prosthetic valve replacement with mechanical prostheses and complicated acute myocardial infarction.

Data on the use of warfarin in children are limited. The initial dose is usually 0.2 mg / kg per day with normal liver function and 0.1 mg / kg per day if liver function is impaired. The maintenance dose is selected in accordance with the MHO indices.The recommended levels of MHO are the same as those of adults. The decision to prescribe warfarin in children should be taken by an experienced specialist. Treatment should be performed under the supervision of an experienced pediatrician.

There are no specific recommendations for taking warfarin in elderly patients. However, older patients should be closely monitored because they have a higher risk of developing side effects.

Disturbance of liver function increases sensitivity to warfarin, because the liver produces clotting factors, and also metabolizes warfarin. This group of patients requires careful monitoring of MHO indicators.

Patients with renal insufficiency do not need any special recommendations for choosing a dose of warfarin. Patients on peritoneal dialysis do not need an additional dose of warfarin.

Pre-, peri- and post-operative anticoagulant therapy is performed as described below. Identify MHO one week prior to the scheduled operation. Stop taking warfarin 1-5 days before surgery. In the case of a high risk of thrombosis, low molecular weight Heparin is administered subcutaneously to the patient for prophylaxis.The duration of pause in taking warfarin depends on MHO. Acceptance of warfarin is discontinued:

• 5 days before surgery with MHO> 4;
• for 3 days before surgery with MHO from 3 to 4;
• 2 days before surgery with MHO from 2 to 3.

It should be determined MHO in the evening before the operation and enter 0.5-1 mg of vitamin K1 orally or intravenously, with INR> 1.8.

Consider the need for infusion of unfractionated heparin or preventive administration of low-molecular-weight heparin on the day of surgery. Subcutaneous administration of low molecular weight heparin should be continued for 5-7 days after surgery with concomitant reconstituted warfarin.

Continue taking warfarin with a normal maintenance dose on the same day in the evening after small surgeries, and the day the patient begins to receive enteral feeding after major surgery.

Side effect

• bleeding;
• increased sensitivity to warfarin after prolonged use;
• anemia;
• nausea, vomiting;
• abdominal pain;
• diarrhea;
• eosinophilia;
• jaundice;
• rash;
• hives;
• itching;
• eczema;
• necrosis of the skin;
• vasculitis;
• hair loss;
• nephritis;
• urolithiasis;
• tubular necrosis;
• reactions of hypersensitivity, manifested as a skin rash,and characterized by a reversible increase in the concentration of liver enzymes, cholestatic hepatitis, vasculitis, priapism, reversible alopecia and calcification of the trachea.

Contraindications

• acute bleeding;
• severe liver disease;
• severe kidney disease;
• acute DVS-syndrome;
• deficiency of proteins C and S;
• thrombocytopenia;
• patients with high risk of bleeding, including patients with hemorrhagic disorders, varicose veins of the esophagus, aneurysm of the arteries, lumbar puncture, peptic ulcer of the stomach and duodenum, with severe wounds (including surgical ones), bacterial endocarditis, malignant hypertension, hemorrhagic stroke, intracranial hemorrhage ;
• pregnancy (1 trimester and the last 4 weeks);
• established or suspected hypersensitivity to the components of the drug.

Application in pregnancy and lactation

Contraindicated use of the drug in the first trimester of pregnancy (use of warfarin is not recommended in the remaining periods of pregnancy, except in cases of emergency) and within the last 4 weeks.

Warfarin rapidly penetrates the placental barrier, it has a teratogenic effect on the fetus (nasal hypoplasia and chondrodysplasia, optic nerve atrophy, cataracts leading to complete blindness, mental retardation, physical development, microcephaly) at 6-12 weeks of gestation. The drug can cause bleeding at the end of pregnancy and during childbirth.

Warfarin is excreted in breast milk in unmeasured quantities and does not affect the coagulating activity of the blood of the infant fed. Therefore, the drug can be used during lactation (breastfeeding).

special instructions

A mandatory condition for therapy with warfarin is strict adherence to the patient's intake of the prescribed dose of the drug. Patients suffering from alcoholism, as well as patients with dementia, may not be able to comply with the prescribed mode of taking warfarin.

Fever, hyperthyroidism, decompensated heart failure, alcoholism with concomitant liver damage, may increase the effect of warfarin.

With hypothyroidism, the effect of warfarin can be reduced.

In the case of renal failure or nephrotic syndrome, the free fraction of warfarin in the blood plasma increases, which,depending on the concomitant diseases, can lead to both an increase and a decrease in the effect. In the case of moderate hepatic insufficiency, the effect of warfarin is enhanced. In all of the above conditions, careful monitoring of the MHO level should be carried out.

Patients receiving warfarin should be prescribed paracetamol, Tramadol or opiates as pain medications.

Do not take warfarin in patients with hereditary intolerance to galactose, a deficiency of the enzyme lactase, a violation of absorption of glucose and galactose.

If it is necessary to achieve a rapid antithrombotic effect, it is recommended to begin treatment with the administration of heparin; then for 5-7 days, combined therapy with heparin and warfarin should be carried out until the target MHO level is maintained for 2 days.

To avoid coumarin necrosis, patients with hereditary deficiency of antithrombotic protein C or S should first be treated with heparin. The concomitant initial loading dose should not exceed 5 mg. The administration of heparin should continue for 5 to 7 days.

In the case of individual resistance to warfarin (it is rare) to achieve a therapeutic effect, 5 to 20 shock doses of warfarin are necessary. If the use of warfarin in such patients is ineffective, other possible causes should be established: simultaneous administration of warfarin with other drugs, inadequate diet, laboratory errors.

Treatment of elderly patients should be carried out with special precautions, as synthesis of coagulation factors and hepatic metabolism in such patients is reduced, resulting in an excessive effect of warfarin.

Drug Interactions

It is not recommended to start or stop taking other medicines, to change the doses of the medications taken without consulting the attending physician.

At simultaneous appointment, it is also necessary to take into account the effects of cessation of induction and / or inhibition of the action of warfarin by other drugs.

The risk of developing severe bleeding increases with the simultaneous use of warfarin with drugs,affecting the platelet level and primary hemostasis: acetylsalicylic acid, clopidogrel, ticlopidine, dipyridamole, most NSAIDs (with the exception of COX-2 inhibitors), antibiotics of the penicillin group in large doses.

Also, combined use of warfarin with drugs with a pronounced inhibitory effect on cytochrome P450 isozymes (including cimetidine, chloramphenicol) should be avoided, and the risk of bleeding increases within a few days. In such cases, cimetidine can be replaced, for example, Ranitidine or famotidine.

The effect of warfarin can be enhanced with simultaneous use with the following medicines: acetylsalicylic acid, allopurinol, amiodarone, azapromazin, azithromycin, alpha and beta interferon, amitriptyline, bezafibrate, vitamin A, vitamin E, glibenclamide, glucagon, gemfibrozil, heparin, grapafloxacin, danazol, dextropropoxyphene, diazoxide, digoxin, disopyramide, disulfiram, zafirlukast, indomethacin, ifosfamide, itraconazole, ketoconazole, clarithromycin, clofibrate, codeine, levamisole, lovastatin, metolazone, methotrexate, met onidazol, miconazole (includingin the form of an oral gel), nalidixic acid, norfloxacin, ofloxacin, omeprazole, oxyphenbutazone, Paracetamol (especially after 1-2 weeks of continuous administration), paroxetine, piroxicam, proguanil, propafenone, propranolol, influenza vaccine, roxithromycin, sertraline, simvastatin, sulfafetrazole, sulfamethisole, sulfamethoxazole / trimethoprim, sulfafenazole, sulfinpyrazone, sulindac, steroid hormones (anabolic and / or androgenic), tamoxifen, tegafur, testosterone, tetracyclines, thienyl acid, tolmetine, trastuzumab, troglide tafon, phenytoin, phenylbutazone, fenofibrate, feprazone, fluconazole, fluoxetine, fluorouracil, fluvastatin, fluvoxamine, flutamide, quinine, quinidine, chlorohydrate, chloramphenicol, celecoxib, cefamandol, cephalexin, cefmenoxime, cefmetazole, cefoperazone, cefuroxime, cimetidine, ciprofloxacin, cyclophosphamide, erythromycin, etoposide, ethanol (alcohol).

Drugs of some medicinal plants (officinal or non-formal) can also enhance the effect of warfarin: for example, ginkgo biloba, garlic (Allium sativum), angelica sinensis, papaya (Carica papaya), sage (Salvia miltiorrhiza); and reduce: for example, ginseng (Panax ginseng), St. John's wort (Hypericum perforatum).

You can not simultaneously take warfarin and any preparations of St. John's wort, and it should be borne in mind that the effect of inducing the effects of warfarin can persist for another 2 weeks after stopping the intake of St. John's wort. In the event that the patient is taking St. John's Wort preparations, MHO should be measured and discontinued. Monitoring of MHO should be thorough, because its level can increase when the St. John's wort is canceled. After this, you can prescribe warfarin.

Also, the action of warfarin can be enhanced by quinine, which is contained in tonic beverages.

Warfarin can enhance the effect of oral hypoglycemic agents of sulfonylurea derivatives.

The effect of warfarin may be weakened when applied simultaneously with azathioprine, aminoglutethimide, barbiturates, valproic acid, vitamin C, vitamin K, glutethimide, griseofulvin, dicloxacillin, disopyramide, carbamazepine, colestyramine, coenzyme Q10, mercaptopurine, mesalazine, mianserin, mitotane, nafcillin, primidon, retinoids, ritonavir, rifampicin, rofecoxib, spironolactone, sucralfate, trazodone, phenazone, chlordiazepoxide, chlorthalidone, cyclosporine.

The use of diuretics in the case of pronounced hypovolemic effects may lead to an increase in the concentration of clotting factors, which reduces the effect of anticoagulants.

In the case of concomitant use of warfarin with other drugs listed in the list below, it is necessary to monitor MHO at the beginning and at the end of treatment, and, if possible, 2-3 weeks after the start of therapy.

Food rich in vitamin K weakens the effect of warfarin (this should be taken into account when developing a diet for drug treatment); a decrease in the absorption of vitamin K, caused by diarrhea or the use of laxatives, potentiates the effect of warfarin. Most of the vitamin K is found in green vegetables, so when treating with warfarin, you should use the following foods with caution: amaranth greens, avocado, broccoli, brussels sprouts, cabbage, canola oil, leaf shayo, onion, coriander, cucumber, chicory, kiwi fruit, lettuce, mint, green mustard, olive oil, parsley, peas, pistachios, red algae, spinach greens, spring onions, soybeans, tea leaves (but not tea-drink), greens turnips, watercress.

Analogues of the drug Warfarin

Structural analogs for the active substance:

• Warfarex;
• Warfarin sodium;
• Warfarin Nycomed;
• Warfarin sodium clathrate;
• Marewan.

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