What is Warfarin?
Warfarin (Warfarina) is a drug used to treat venous thrombosis, pulmonary embolism and prosthetic heart valves. The product ingredients are: Warfarin potassium, Warfarin sodium.
The brand names of Warfarin in United States are: Coumadin, Jantoven
Mechanism of action (MOA) of Warfarin
It prevents the formation in liver of active factors of coagulation II, VII, IX and X by inhibition of gamma-carboxylation of precursor proteins mediated by vit. K.
Therapeutic indications, uses and benefits of Warfarin
- Prophylaxis and/or treatment of venous thrombosis.
- Pulmonary embolism.
- Prophylaxis and/or treatment of thromboembolic complications associated with atrial fibrillation and/or substitution of cardiac valves.
- After AMI, it reduces the risk of death due to recurrent myocardial infarction or thromboembolic episodes such as stroke or systemic embolization.
Posology of Warfarin
In general: initial dose, 2-5 mg/day; maintenance, 2-10 mg/day.
Individualize doses according to INR. The INR to reach is between 2,0-3,5 according to pathology.
Contraindications of Warfarin
- Lack of cooperation on the part of the patient.
- Hemorrhagic diathesis and/or hematic dyscrasia.
- Organic lesions susceptible to bleeding.
- Recent or planned surgical interventions in the CNS, ophthalmological operations or operations that expose large surfaces of tissue.
- Gastroduodenal ulcer or haemorrhages in gastrointestinal, urogenital or respiratory tracts, cerebrovascular haemorrhages, pericarditis, pericardial effusions, slow endocarditis.
- Severe high blood pressure; severe lesions of the liver and renal parenchyma.
- Increased fibrinolytic activity (e.g. after lung, prostate, etc. operations).
- High doses of NSAIDs, miconazole (general route and oral gel), phenylbutazone (general route), high doses of ASAs and other salicylates.
Warnings and precautions with Warfarin
- Risk of: hemorrhages, necrosis (if there is necrosis, substitute heparin), release of emboli or atheromatous plaques.
- Moderate-severe renal insufficiency, moderate-severe hepatic insufficiency, moderate-severe high blood pressure.
- Infectious diseases or alterations of intestinal flora; catheters; deficiency in anticoagulant response mediated by protein C or its cofactor, protein S (risk of tissue necrosis); monitor INR.
- There are no data to support its use in children; suspend treatment if calcifilaxis appears (greater risk in advanced renal disease on dialysis).
Warfarin is contraindicated in severe liver parenchymal disorders.
Caution in moderate to severe liver failure.
Warfarin is contraindicated in severe renal parenchymal disorders.
Caution in moderate to severe renal insufficiency.
Effect inhibited by: enzyme inducers (aminoglutethimide, carbamazepine, phenazone, griseofulvin, phenobarbital, secobarbital, rifampicin, H. perforatum), drugs that reduce their absorption (sucralfate, ascorbic acid), vit. K, ginseng, foods rich in vit. K (cereals, broccoli, cabbage, carrots, poultry giblets).
Effect enhanced by:
- Enzyme inhibitors (allopurinol, dextropropoxyphene, tramadol, amiodarone, ciprofloxacin, clarithromycin, erythromycin, norfloxacin, ofloxacin, pefloxacin, chloramphenicol, cimetidine, omeprazole, ranitidine, cisapride, disulfiram, fluvastatin, lovastatin, simvastatin, fluconazole, fluorouracil, fluoxetine, fluvoxamine, interferon alpha and beta, isoniazid, itraconazole, lornoxicam, metronidazole, saquinavir, tamoxifen, viloxazine, inactive flu viruses).
- Drugs that displace it from its binding to plasma proteins (ethacrynic acid, nalidixic acid, diclofenac, phenylbutazone, feprazone, ibuprofen, ketoprofen, mefenamic acid, sulindaco, benziodarone, bicalutamide, carnitine, gemfibrozil, chloral hydrate, miconazole, ac. valproic).
- Decreased availability of vitamin K (levothyroxine, neomycin, cefamandol, clofibrate, stanozolol).
- Drugs that decrease the synthesis of coagulation factors (danazol, paracetamol, quinidine, quinine, vit. E, ethanol).
- AAS, diflunisal.
- Doxycycline, tetracycline (hypoprothrombinemic).
- Clindamycin: may increase anticoagulant activity with increased values of coagulation tests (TP/INR) and/or bleeding.
- Others: benzbromarone, propranolol, piracetam.Increases prothrombin time with: sulfamethoxazole, flutamide.
Decreases prothrombin time with: chlorthalidone, spironolactone.
Variable anticoagulant effect by: oral contraceptives, phenytoin, disopyramide, cholestyramine.
Pregnancy and Warfarin
Not recommended, crosses the placenta.
Congenital malformations and other adverse effects on fetal development have been described, including severe nasal hypoplasia, chondrodysplasia punctata, optic atrophy, microcephaly and growth retardation in children born to mothers undergoing this medication during the first trimester.
Virtually no warfarin is detected in breast milk, so no unwanted effects on the infant are to be feared.
Children fed milk from mothers treated with warfarin do not suffer changes in prothrombin times.
Adverse reactions and side effects of Warfarin
Bleeding into any organ.
If INR is < 6, no bleeding, discontinue therapy. If INR is > 6, no major bleeding: 0.5 mg vit. K1 in 20-30 min continuous perfusion.
Increase to 1 mg if INR is >10. If severe bleeding occurs: 10-20 mg vit. K1 in continuous slow perfusion of 1 h, with transfusion of plasma, blood or factor IX complex.
⭐⭐⭐⭐⭐ VIDEO OF WARFARIN/JANTOVEN (DRUG)
Source: The content of this active ingredient has been written taking into account the clinical and molecular information of all medicines authorised and marketed in the United States under the Unique Ingredient Identifier (UNII) by the Substance Registration System (SRS) of the Food and Drug Administration (FDA) and the United States Pharmacopeia (USP).
In order to know in detail the information authorized by the FDA for each drug, you should consult the corresponding medication guide authorized by the FDA.