Trials of patient-based self-monitoring and dose-adjustment of warfarin therapy are under way, but currently this cannot be recommended. Pre-conception counselling is needed for women on long-term treatment. Women of childbearing age should be informed of the potential dangers of warfarin in pregnancy. These are a useful supplement to the doctor's advice. – remain with one or other of the currently available brands of warfarin (Coumadin or Marevan), as these have not been formally shown to be bioequivalent and are therefore not interchangeable.īooklets aimed at patient education are available from all pharmacies. – keep a written record of INR results and warfarin dosage – have more frequent measurements of their INR when starting or stopping other medications, either prescribed or complementary – report any signs of bleeding while on warfarin Patients who have a poor understanding of the indications and potential adverse effects are more likely to be non-compliant than those who receive education about warfarin. Unfractionated heparin and low molecular weight heparin are alternatives that do not cross the placenta. There may be a place for mid-trimester warfarin in pregnant women with prosthetic heart valves, but this choice should be made only after a full discussion of the implications with the patient. Warfarin in pregnancy is teratogenic and causes peripartum bleeding in mother and child, so it is generally contraindicated in pregnancy. 2Bleeding in this report was called `major' if it was fatal, was intracranial, retroperitoneal or involved a joint, required surgery, led to a haemoglobin fall of 2 g/dL or more, and/or required the transfusion of two or more units of blood. In one study, the annual risk of major bleeding was 2.9% for patients older than 70 years, while no major bleeds occurred in patients under 50 years old. – change in interacting medications (see Table 4)Īge is one of the strongest risk factors for bleeding. – gastrointestinal haemorrhage within the last 18 months Table 2 Risk factors for major bleeding in patients on warfarin Although the bleeding risk increases as the INR (International Normalised Ratio) increases, 50% of bleeding episodes occur while the INR is less than 4.0. Bleeding complications occur in 3-10% of patients on warfarin per year, but most bleeds are minor. 1A patient's risk of bleeding is greatest in the first few months after starting warfarin. The major adverse effect of warfarin is an increased bleeding tendency and many factors can increase the risk ( Table 2). – congestive heart failure or dilated cardiomyopathy – atrial fibrillation without structural heart disease in patients >50 years old – atrial fibrillation associated with valvular heart disease – recurrent deep vein thrombosis or pulmonary embolism – pulmonary embolism within the last six months – deep vein thrombosis within the last three months The common indications for warfarin therapy The decision to start warfarin depends on an assessment of each patient's balance between the harmful effects and the benefits of anticoagulation. There are many indications for warfarin therapy ( Table 1). Its pharmacology is complicated and many factors need to be considered in the optimal management of each patient. As the population ages and more trials show its benefits, more and older patients will be started on warfarin. ![]() Warfarin is one of the commonest causes of death related to prescription drugs, but when used appropriately it is one of the most beneficial drugs.
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