LENNON - WARFARIN 5 mg TABLETS
(and dosage form):
LENNON - WARFARIN 5 mg TABLETS
[Ed. NB. product name change to ASPEN WARFARIN - Dec 2010]
Each tablet contains Warfarin Sodium Clathrate equivalent to 5 mg Warfarin Sodium.
A 8.2 Anticoagulants
Warfarin is a coumarin-type anticoagulant and acts by depressing synthesis of Vitamin-K dependent coagulation factors in the liver. The resultant in vivo effect is a sequential depression of Factors VII, IX, X and II.
After oral administration, absorption is essentially complete and maximal plasma concentrations are reached in 2 to 8 hours. Approximately 99% is bound to albumin in the plasma. The half-life ranges from 20 to 60 hours with a mean of 40 hours. The duration of action is 2 to 5 days. Food in the gastrointestinal tract can decrease the rate of absorption. Warfarin is transformed to inactive metabolites by the liver and kidneys and these are excreted in the urine and stool.
Prevention and management of deep venous thrombosis and pulmonary embolism.
Prevention of thromboembolism in:
prosthetic heart valves
post myocardial infarction
In the treatment of transient ischaemic attacks.
Should not be used in patients with:
Peptic ulcers or other gastrointestinal disease involving bleeding
Conditions involving bleeding from respiratory or genito-urinary tract
Severe wounds (including surgical)
Impaired liver function
Impaired kidney function
Aneurysm - cerebral, aortic
Pericarditis, pericardial effusion
Neuro- or ophthalmic surgery - recent or contemplated
Surgery involving large exposed raw surfaces
Vitamin C deficiency
Major regional block anaesthesia
Inadequate laboratory facilities or lack of patient co-operation
Breast feeding mothers
Warfarin is a recognised teratogen. It should be avoided in pregnancy. (See warnings)
Safety in children younger than 18 years has not been established.
Abrupt cessation of anticoagulant therapy is not recommended. The dose should be tapered over three to four weeks.
Special care is required in the elderly; in patients with Vitamin K deficiency and in patients with hyperthyroidism.
Dosage should be individualised for each patient and periodic determinations of prothrombin time should be done. (see dosage and directions for use).
The management of patients who undergo dental and surgical procedures requires close liaison between doctors, surgeons and dentists. An adjustment of dosage may be necessary.
Warfarin should be used with caution in patients with:
- prolonged dietary deficiency;
- infectious diseases or disturbances of intestinal flora, sprue, antibiotic therapy;
- polycythaemia vera, vasculitis, severe diabetes, allergic or anaphylactic disorders.
Non-steroidal anti-inflammatory agents should not be used with warfarin.
DOSAGE AND DIRECTIONS FOR USE:
The administration and dosage of Warfarin must be individualised for each patient according to the patient's sensitivity as indicated by the prothrombin time (PT) or international normalised ratio. (INR)
PT measurements should be carried out before treatment, on the 2nd and 3rd days of treatment and then on alternate days until the maintenance dose is established. Thereafter the patient should be monitored monthly.
Satisfactory levels of PT or INR for maintenance, vary with the condition treated and the risk of thromboembolism.
INR 2.0 - 2.5 (PT ratio 1.3 -1.5)
Prophylaxis of DVT including surgery in high risk patients.
INR 2.0 - 3.0 (PT ratio 1.3 -1.5)
Prophylaxis of DVT in hip surgery and fractured femur operations.
Prevention of thromboembolism in myocardial infarction, mitral stenosis with embolism, atrial fibrillation, tissue prosthetic heart valves.
Treatment of DVT, pulmonary embolism, transient ischaemic attacks, systemic embolism.
INR 3.0 - 4.5 (PT ratio 1.5 - 2.0)
Recurrent DVT and pulmonary embolism. Arterial disease including myocardial infarction.
Mechanical prosthetic heart valves.
The correlation between the INR and the PT ratio is based on thromboplastin with an International sensitivity index of 2.3.
Initial doses are usually within the range of 10 - 15 mg daily for 3 days. Maintenance doses range from 2 -10 mg daily.
Doses should be given at the same time each day.
SIDE-EFFECTS AND SPECIAL PRECAUTIONS:
Haemorrhage from almost any organ of the body with the consequent effects of haematomas as well as anaemia. Skin necrosis may occur.
Purple toe syndrome - a reversible, sometimes painful, bluish discoloration of the toes may occur.
Other effects include alopecia, fever, nausea, vomiting, diarrhoea, hypersensitivity reactions, and skin reactions.
Patients should be given detailed instructions concerning their medication, the importance of compliance and advice concerning modification of their life style if necessary.
The possibility of interactions should be explained. The need for modification of therapy before elective operative procedures or in women contemplating pregnancy should be discussed. Patients should carry an anticoagulant card or other proof that they are on anticoagulants.
A wide variety may occur, increasing or diminishing the anticoagulant response with different mechanisms involved. Not all interactions have been identified and some interacting agents do so by more than one mechanism therefore the nett effect may be unpredictable.
Mechanisms of interaction include:
* displacement from albumin binding sites.
* altering metabolism of agents by inhibition or induction of hepatic microsomal enzymes.
* interference with absorption or metabolism of warfarin or vitamin K.
* additional anticoagulant effects by agents that inhibit platelet function.
Interactions of major significance:
Agents that enhance the anticoagulant effect:
sulphonamides, sulphonylurea-type antidiabetic agents, clofibrate, cimetidine, phenylbutazone and other pyrazolones, anabolic steroids, sulphinpyrazone, aspirin and other NSAIDS, thyroid hormones, disulfiram and amiodarone.
Agents that diminish the anticoagulant effect:
barbiturates, rifampicin and glutethimide. Vitamin K is a specific antagonist.
Interactions of theoretical significance (require careful monitoring of the prothrombin time)
Agents that may enhance the anticoagulant effect:
Allopurinol, danazol, diazoxide, metronidazole, aminoglycosides, alcohol, miconazole, triclofos, chloral hydrate, chloramphenicol, phenytoin, erythromycin, quinidine, dextropropoxyphene, Vitamin E and glucagon.
Agents that may diminish the anticoagulant effect:
Oral contraceptives (oestrogens), carbamazepine, griseofulvin, glucocorticoids and cholestyramine.
The following factors may be responsible for an increase in prothrombin time:
Carcinoma, collagen disease, congestive heart failure, diarrhoea, elevated temperature, hepatic disorders, infectious hepatitis, jaundice, poor nutritional state.
The following factors may be responsible for a decrease in prothrombin time:
Diabetes mellitus, oedema, hereditary resistance to warfarin therapy, hyperlipaemia, hypothyroidism.
SYMPTOMS OF OVERDOSAGE AND PARTICULARS OF ITS TREATMENT:
Excessive bleeding may occur.
If an excessively long PT or INR occurs or there is minor bleeding, omission of one or several doses of warfarin may be sufficient to return levels to the therapeutic range.
If significant bleeding occurs small doses of Vitamin K (1-5 mg) orally may suffice. Life threatening bleeding may be treated with Vitamin K (20-40 mg) by slow intravenous administration together with fresh frozen plasma (at least 1 litre for an adult)
A flat, pink, speckled, circular tablet scored on one side and bevelled edged.
Securitainers of 100
Store below 25°C in airtight containers.
Protect from light.
KEEP OUT OF REACH OF CHILDREN.
NAME AND BUSINESS ADDRESS OF APPLICANT:
7 Fairclough Road
DATE OF PUBLICATION OF THIS PACKAGE INSERT:
18 October 1996
Updated on this site: October 2002
Current: September 2004
Source: Community Pharmacy
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