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WARFARIN is a brand name for Warfarin. The medicine, its uses, side effects and dosage are the same regardless of brand.
Used for: Prophylaxis of systemic embolism in patients with rheumatic heart disease and atrial fibrillation. Prophylaxis after insertion of prosthetic heart valves. Prophylaxis and treatment of venous thrombosis and pulmonary embolism. Transient attacks of cerebral ischaemia.
Verbatim from this product's MHRA label. Tap a section to expand.
Posology Adults:
The typical induction dose is 10 mg daily for 2 days but this should be tailored to individual requirements. The daily maintenance dose is usually 3 to 9 mg taken at the same time each day. The exact maintenance dose depends on the prothrombin time or other appropriate coagulation tests.
Control tests should be made at regular intervals and the maintenance dose should be adjusted according to the results obtained. Once the maintenance dose is established, it is rarely necessary to alter it. In emergencies, anticoagulant therapy should be initiated with heparin and Warfarin together.
Concomitant therapy with heparin affects the results of control tests, and should be discontinued at least six hours before the first test is carried out.
Elderly:
As for adults, but dosage may need to be lowered. The elderly are generally more sensitive to the effects of warfarin and often require a smaller dose.
Paediatric population:
Warfarin Tablets are not recommended for use in children due to insufficient data on safety and efficacy. Method of administration Oral.
Frequency categories are unknown for the following reported adverse reactions and therefore have not been included. 4) (unknown frequency) Investigations Unexplained drop in haematocrit; haemoglobin decreased Skin necrosis is a rare but serious side effect of warfarin.
It occurs mainly in obese, female patients, usually within 3 to 10 days of starting therapy, and is associated with the use of high induction doses. Patients with protein C or protein S deficiency are at particular risk. Initially, the lesions consist of painful, indurated, reddened areas, which progress through a stage of blood- filled blisters into well-demarcated blackened necrotic patches.
Areas of skin with underlying fatty tissue, such as breasts, flanks and buttocks are most often affected. Pain in a particular area of skin is a premonitory symptom, and withdrawal of the oral anticoagulant at this stage, reversal of its effects with vitamin k or fresh frozen plasma, and the use of heparin may limit the extent of tissue damage.
‘Purple toes’ which is a rare complication of warfarin therapy. Typically, the syndrome presents 3 to 8 weeks after initiation of warfarin therapy as a sometimes painful blue-tinged discoloration of the plantar aspects and sides of the toes.
Cholesterol emboli released from atheromatous plaques have been implicated as the cause. If the syndrome occurs, it is recommended that warfarin therapy be withdrawn, if possible, as the affected tissue may undergo ischaemic necrosis.
Reporting of suspected adverse reactions Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. uk/yellowcard or search for MHRA Yellow Card in the Google Play or Apple App Store.
Most adverse events reported with warfarin are a result of over anticoagulation therefore it is important that the need for therapy is reviewed on a regular basis and therapy discontinued when no longer required. Patients should be given a patient-held information booklet (‘warfarin card’) and informed of symptoms for which they should seek medical attention.
Monitoring When warfarin is started using a standard dosing regimen the INR should be determined daily or on alternate days in the early days of treatment. Once the INR has stabilised in the target range the INR can be determined at longer intervals.
g. patients with severe hypertension, liver or renal disease. Patients for whom adherence may be difficult should be monitored more frequently. For patients with any impairment that may influence their ability to take the correct dosage safely, the assistance of a carer to administer the dose may be required.
Thrombophilia Patients with protein C deficiency are at risk of developing skin necrosis when starting warfarin treatment. In patients with protein C deficiency, therapy should be introduced without a loading dose of warfarin even if heparin is given.
Patients with protein S deficiency may also be at risk and it is advisable to introduce warfarin therapy slowly in these circumstances. Risk of haemorrhage The most frequently reported adverse effect of all oral anticoagulants is haemorrhage.
g. concomitant NSAID use, recent ischaemic stroke, bacterial endocarditis, previous gastrointestinal bleeding). 3. g. 5).
Genetic factors:
Genetic variability particularly in relation to CYP2C9 and VKORC1 can significantly affect dose requirements for warfarin. If a family association with these polymorphisms is known extra care is warranted. All patients treated with warfarin should have INR monitored regularly.
4).
Not medical advice. Always read the patient information leaflet and follow your prescriber or pharmacist.
Other brands of Warfarin in United Kingdom.
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Those at high risk of bleeding may benefit from more frequent INR monitoring, careful dose adjustment to desired INR, and a shorter duration of therapy. Patients should be instructed on measures to minimise risk of bleeding and to report immediately to physicians, signs and symptoms of bleeding.
Checking the INR and reducing or omitting doses depending on INR level is essential, following consultation with anticoagulation services if necessary. If the INR is found to be too high, reduce dose or stop warfarin treatment; sometimes it will be necessary to reverse anticoagulation.
INR should be checked within 2–3 days to ensure that it is falling. Any concomitant anti-platelet drugs should be used with caution due to an increased risk of bleeding. Haemorrhage Haemorrhage can indicate an overdose of warfarin has been taken.
9. Unexpected bleeding at therapeutic levels should always be investigated and INR monitored. 9). Bleeding may occur at therapeutic INR values, in which case the possibility of an underlying condition that predisposes the haemorrhage should be investigated.
Calciphylaxis Calciphylaxis is a rare syndrome of vascular calcification with cutaneous necrosis, associated with high mortality. The condition is mainly observed in patients with end-stage renal disease on dialysis or in patients with known risk factors such as protein C or S deficiency, hyperphosphataemia, hypercalcaemia or hypoalbuminaemia.
Rare cases of calciphylaxis have been reported in patients taking warfarin, also in the absence of renal disease. In case calciphylaxis is diagnosed, appropriate treatment should be started and consideration should be given to stopping treatment with warfarin.
Ischaemic stroke Anticoagulation following an ischaemic stroke increases the risk of secondary haemorrhage into the infarcted brain. In patients with atrial fibrillation long term treatment with warfarin is beneficial, but the risk of early recurrent embolism is low and therefore a break in treatment after ischaemic stroke is justified.
Warfarin treatment should be re-started 2–14 days following ischaemic stroke, depending on the size of the infarct and blood pressure. In patients with large embolic strokes, or uncontrolled hypertension, warfarin treatment should be stopped for 14 days.
5. For surgery where there is a risk of severe bleeding, warfarin should be stopped 3days prior to surgery. g. 5 and heparin therapy should be started. If surgery is required and warfarin cannot be stopped 3 days beforehand, anticoagulation should be reversed with low-dose vitamin K.
The timing for re-instating warfarin therapy depends on the risk of post- operative haemorrhage. In most instances warfarin treatment can be re-started as soon as the patient has an oral intake. g, tooth extraction. Active Peptic ulceration Due to a high risk of bleeding, patients with history of peptic ulcers should be treated with caution.
Such patients should be reviewed regularly and […]