Warfarin
Warfarin: instructions for use and reviews
- 1. Release form and composition
- 2. Pharmacological properties
- 3. Indications for use
- 4. Contraindications
- 5. Method of application and dosage
- 6. Side effects
- 7. Overdose
- 8. Special instructions
- 9. Application during pregnancy and lactation
- 10. Drug interactions
- 11. Analogs
- 12. Terms and conditions of storage
- 13. Terms of dispensing from pharmacies
- 14. Reviews
- 15. Price in pharmacies
Latin name: Warfarin
ATX code: B01AA03
Active ingredient: Warfarin (Warfarin)
Manufacturer: Kanonpharma production CJSC, Ozon LLC, Obolenskoe - pharmaceutical company (Russia)
Description and photo update: 2019-07-08
Prices in pharmacies: from 52 rubles.
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Warfarin is an indirect anticoagulant.
Release form and composition
Warfarin is produced in the form of tablets, 5, 10, 14, 20, 25 pieces in blisters, 50, 100, 250 pieces in cans.
The composition of 1 tablet contains the active substance - warfarin sodium in an amount of 2.5 mg.
Pharmacological properties
Pharmacodynamics
Warfarin is an indirect anticoagulant and a coumarin derivative. It inhibits the production of vitamin K-dependent coagulation factors (II, VII, IX and X) and anticoagulant proteins S and C in the liver. The anticoagulant effect appears 36–72 hours after the start of the drug intake. The maximum therapeutic effect is achieved within 5-7 days after the start of administration. Cancellation of the drug leads to the restoration of the activity of vitamin K-dependent factors of blood clotting after 4–5 days.
Pharmacokinetics
After oral administration, warfarin is absorbed from the gastrointestinal tract at a high rate. It is also characterized by absorption through the skin. The compound binds to plasma proteins to a high degree, penetrates the placental barrier and is excreted in breast milk in small concentrations.
Warfarin is a racemic mixture of isomers metabolized in the liver. The S isomer is more active and metabolized in a shorter period of time than the R isomer. Metabolism is carried out with the participation of isoenzymes of the cytochrome P450 system - 3A4, 2C9, 2C19, 2C8, 2C18, 1A2.
The half-life is on average 40 hours. In the terminal phase, this indicator increases to about 1 week. The clearance of the R isomer is typically half that of the S isomer. With similar V d values, the half-life of the R-isomer is 37–89 hours and exceeds that of the S-isomer (21–43 hours).
Laboratory studies using a radioactive label have shown that after a single oral dose, approximately 92% of warfarin is excreted through the kidneys in the form of metabolites and only a small amount is excreted unchanged.
Indications for use
Warfarin is prescribed for the treatment and prevention of thrombosis and embolism in blood vessels. The indications for use are the following diseases / conditions:
- Pulmonary embolism and acute venous thrombosis;
- Repeated pulmonary embolism;
- Recurrent myocardial infarction;
- Postoperative or recurrent venous thrombosis;
- Prosthetics of heart valves and blood vessels (possibly in combination with acetylsalicylic acid);
- Thrombosis of the cerebral, coronary and peripheral arteries;
- Secondary prevention of thromboembolism and thrombosis in atrial fibrillation and after myocardial infarction.
Warfarin is also used as an adjunct for the medical or surgical treatment of thrombosis and for electrical cardioversion of atrial fibrillation.
Contraindications
Contraindications to the use of Warfarin are:
- Pathological changes in the blood;
- Diseases and conditions accompanied by a high risk of bleeding;
- Recently performed craniocerebral operations;
- Ophthalmic operations;
- Bleeding tendencies in ulcerative lesions of the gastrointestinal tract, diseases of the genitourinary and respiratory system;
- Surgical interventions for trauma with an extensive operating field;
- Aneurysms;
- Cerebrovascular hemorrhages;
- Severe kidney or liver disease;
- Pericardial effusion, bacterial endocarditis, pericarditis;
- Severe arterial hypertension;
- Acute disseminated intravascular coagulation syndrome;
- Spinal puncture or other diagnostic procedures, accompanied by the potential threat of uncontrolled bleeding;
- Malignant arterial hypertension;
- Blockade, extensive regional anesthesia;
- Lack of observation of elderly patients;
- Inadequate laboratory conditions for monitoring the patient;
- Disorganization of the patient;
- Psychoses;
- Alcoholism;
- Pregnancy;
- Threatened abortion.
Inactive warfarin is excreted in breast milk. In children whose mothers took the drug during lactation, no changes in prothrombin time were found. The effect of the drug in premature infants has not been studied.
The efficacy and safety of warfarin in children under 18 years of age has not been established.
Instructions for the use of Warfarin: method and dosage
The tablets are taken orally at 2-10 mg per day. The daily dosage is determined by the blood coagulation parameters, the patient's response to treatment, and the clinical situation.
Side effects
When using Warfarin, it is possible to develop violations from various systems and organs:
- Digestive system: cholestasis, nausea, hepatitis, diarrhea, vomiting, increased activity of liver enzymes, abdominal pain, jaundice;
- Blood coagulation system: hematomas, bleeding, anemia; rarely - necrosis of the skin and other tissues due to local thrombosis;
- Central nervous system: headache, lethargy, fatigue, asthenia, taste disturbances, dizziness;
- Cardiovascular system: vasculitis, purple discoloration of the toes, chills, feeling of coldness, paresthesia;
- Respiratory system: rarely - tracheo-bronchial or tracheal calcification with prolonged therapy (clinical significance has not been established);
- Allergic reactions: itching, swelling, skin rash, urticaria, fever;
- Dermatological reactions: bullous rash, dermatitis, alopecia.
Overdose
Symptoms of chronic intoxication with an overdose of Warfarin are the presence of blood streaks in the urine and feces, bleeding from the nose or gums, hemorrhages in the skin, excessive bleeding during menstruation, heavy and prolonged bleeding with minor damage to the epidermis.
If the prothrombin time exceeds 5% and there are no other possible sources of bleeding (nephrourolithiasis, etc.), there is no need to correct the dosage regimen. With minor bleeding, the dose of Warfarin is reduced or the drug is canceled for a short period. If the patient develops heavy bleeding, vitamin K is prescribed until the coagulant activity is fully restored. Threatening bleeding is an indication for transfusion of fresh frozen plasma, fresh blood, or concentrates of prothrombin complex factors.
special instructions
The risk of bleeding increases with prolonged and intensive anticoagulant therapy.
During treatment, it is necessary to control the dosage and periodically determine the prothrombin time and other coagulation parameters.
With the simultaneous use of warfarin with other drugs, it is necessary to take into account the high probability of drug interaction.
Therapy may increase the risk of atherosclerotic plaque particle embolism.
Warfarin should be used with extreme caution and only after careful analysis of the benefit-risk ratio should be used in the following cases:
- Injury that can lead to internal bleeding
- Infectious diseases (including sprue) or dysbiosis associated with the use of antibiotics;
- Indwelling catheters;
- Trauma with extensive bleeding surface or surgery;
- Expected or known protein C deficiency;
- Moderate to severe arterial hypertension;
- Anaphylactic reactions, severe and moderate allergic reactions;
- Vasculitis, polycythemia vera, severe diabetes.
Patients with congestive heart failure require dose adjustments and more frequent laboratory monitoring.
It is not recommended to concomitantly use Warfarin with streptokinase and urokinase.
During therapy, special supervision is required for elderly patients, as well as for people with mental disabilities.
It is believed that renal clearance does not significantly affect the intensity of action of warfarin.
With impaired liver function, a decrease in the metabolism of Warfarin and a potentiation of its effects can be observed, which is associated with a violation of the synthesis of coagulation factors.
Application during pregnancy and lactation
According to the instructions, Warfarin is not prescribed to pregnant women due to the revealed teratogenic effect and the high risk of bleeding in the fetus and its death.
The drug in a small amount penetrates into breast milk and practically does not affect blood clotting in a child, therefore, the appointment of Warfarin during lactation is allowed, however, during the first 3 days after the start of treatment, it is recommended to refrain from breastfeeding.
Drug interactions
Simultaneous use of Warfarin with other drugs:
- Anticholinergics - possible impairment of attention and memory in elderly patients;
- Drugs with antiplatelet activity and anticoagulants - the risk of bleeding increases;
- Hypoglycemic agents sulfonylurea derivatives - their hypoglycemic effect may be enhanced;
- Inhibitors of liver microsomal enzymes - the risk of bleeding increases and the anticoagulant effect of Warfarin increases;
- Cyclosporine - there is a mutual decrease in effects;
- Ticlopidine - a case of liver damage has been described (the effect of Warfarin does not change);
- Ethacrynic acid - may increase hypokalemia, diuretic effect;
- Cholestyramine - reduced bioavailability and absorption of Warfarin;
- Phenytoin - there are reports of an initial increase in anticoagulant activity followed by a decrease;
- Phenazone - the concentration of Warfarin in the blood plasma decreases;
- Enoxacin - the clearance of the R-isomer (not the S-isomer) decreases while maintaining the prothrombin time;
- Trazodone, fluoxetine, vitamin E - there is evidence of an increase in the action of warfarin.
The anticoagulant effect of warfarin is reduced by: mianserin, acitretin, coenzyme Q10, inducers of microsomal liver enzymes (including phenytoin, barbiturates, carbamazepine), glucagon, rifampicin, paracetamol, glutethimide, vitamins, griseofulkravin, dicfloxacil, ken aminoglutethimide, glutethimide, cholestyramine, diuretics (spironolactone and chlorthalidone), mitotane, mercaptopurine, ginseng preparations, cisapride.
An increase in the anticoagulant effect of Warfarin and an increase in the risk of bleeding is possible with its simultaneous use with: pyrazolone derivatives (including sulfinpyrazone, phenylbutazone), heparin, non-steroidal anti-inflammatory drugs (including acetylsalicylic acid), paracetamol, a combination and codeine, dextropropoxyphene, antiarrhythmics (including with quinidine, amiodarone, moracizin, propafenone), antifungal and antimicrobial agents (including with metronidazole, clarithromycin, chloramphenicol, cefmetazole, cefamicon, tssefromazole roxithromycin, azithromycin, co-trimoxazole, miconazole, ketoconazole, itraconazole, ofloxacin, fluconazole, nalidixic acid, norfloxacin, doxycycline, ciprofloxacin,aminosalicylic acid, tetracyclines, isoniazid, neomycin, benzylpenicillin, aztreonam), quinine, glibenclamide, valproic acid, cyclophosphamide, proguanyl, fluorouracil, methotrexate, with combinations of vindesosphine or simfenomide, and etoposfine in chronic hepatitis C), saquinavir, interferon beta, gemfibrozil, clofibrate, fenofibrate, danazol, ciprofibrate, cimetidine, fluvastatin, lovastatin, piracetam, tramadol.interferon alpha (in chronic hepatitis C), saquinavir, interferon beta, gemfibrozil, clofibrate, fenofibrate, danazol, ciprofibrate, cimetidine, fluvastatin, lovastatin, piracetam, tramadol.interferon alfa (in chronic hepatitis C), saquinavir, interferon beta, gemfibrozil, clofibrate, fenofibrate, danazol, ciprofibrate, cimetidine, fluvastatin, lovastatin, piracetam, tramadol.
With the simultaneous use of warfarin with tocopherol, disopyramide, tricyclic antidepressants, felbamate, allopurinol, terbinafine, chloral hydrate, dipyridamole, ascorbic acid, ranitidine, data on drug interactions are ambiguous.
In patients with chronic alcoholism taking disulfiram, there is an increase in the effects of warfarin.
In case of accidental intake of large amounts of alcohol, an increase in the effect of Warfarin may also be observed.
With regular intake of alcohol, a decrease in the effects of the drug is possible, which may be associated with the induction of liver enzymes. With liver damage, the effects of Warfarin may be enhanced.
Analogs
Warfarin analogues are: Warfarex, Warfarin Nycomed, Warfarin-OBL, Marevan, Ksarelto, Pradaksa.
Terms and conditions of storage
Store in a dark, dry place out of reach of children at temperatures up to 25 ° C.
Shelf life is 2 years.
Terms of dispensing from pharmacies
Dispensed by prescription.
Reviews about Warfarin
Reviews about Warfarin vary significantly. Many people take the drug for an extended period of time as an effective blood thinner. However, some patients note adverse reactions accompanying therapy with Warfarin: periodic bouts of nausea, dizziness, increased bleeding. In this case, the treatment gives good results only if the treatment regimen is followed and the condition of the body is constantly monitored.
The price of Warfarin in pharmacies
The average price for Warfarin in a dosage of 2.5 mg is 115–130 rubles for a pack of 50 tablets and 170–190 rubles for a pack of 100 tablets.
Warfarin: prices in online pharmacies
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Drug name Price Pharmacy |
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Warfarin 2.5 mg tablets 50 pcs. 52 RUB Buy |
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Warfarin 2.5 mg tablets 50 pcs. 52 RUB Buy |
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Warfarin 2.5 mg tablets 50 pcs. 52 RUB Buy |
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Warfarin 2.5 mg tablets 100 pcs. RUB 63 Buy |
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Warfarin 2.5 mg tablets 100 pcs. 73 rbl. Buy |
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Warfarin Nycomed 2.5 mg tablets 50 pcs. RUB 90 Buy |
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Reviews Warfarin Nycomed RUB 90 Buy |
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Warfarin tablets 2.5mg 100 pcs. 102 RUB Buy |
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Warfarin Nycomed 2.5 mg tablets 100 pcs. 143 r Buy |
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Reviews Warfarin Nycomed 143 r Buy |
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Warfarin Nycomed tablets 2.5mg 100 pcs. 147 RUB Buy |
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Maria Kulkes Medical journalist About the author
Education: First Moscow State Medical University named after I. M. Sechenov, specialty "General Medicine".
Information about the drug is generalized, provided for informational purposes only and does not replace the official instructions. Self-medication is hazardous to health!
