Warfarin is commonly used in general practice to treat and prevent thrombosis in a range of clinical settings. It acts by antagonising the action of vitamin K resulting in production of defective clotting proteins. It is cleared via the cytochrome P450 enzymes in the liver and is subject to interactions with a large number of drugs. It is extremely important to increase the frequency of International Normalised Ratio (INR) monitoring whenever a drug is started or stopped while a patient is on warfarin.
Warfarin is a commonly used medication for the prevention
and treatment of venous thromboembolism. It can be
challenging for both the patient and the prescriber to
manage at times.
To describe the mechanism of action of warfarin, and
to discuss the indications for warfarinisation, the risks
associated with warfarin use, and some of its drug
The common indications for warfarinisation are atrial
fibrillation, venous thromboembolism and prosthetic heart
valves. Contraindications include absolute and relative
contraindications, and an individualised risk-benefit
analyses is required for each patient. There are many
interactions with warfarin, including pharmacokinetic and
pharmacodynamic. Pharmacokinetic interactions can be
monitored by using International Normalised Ratio levels.
Pharmacodynamic interactions require knowledge by the
prescriber to predict any interactions with warfarin, and
International Normalised Ratio monitoring assists.
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