Drug Groups

approved

Description

An anticoagulant that acts by inhibiting the synthesis of vitamin K-dependent coagulation factors. Warfarin is indicated for the prophylaxis and/or treatment of venous thrombosis and its extension, pulmonary embolism, and atrial fibrillation with embolization. It is also used as an adjunct in the prophylaxis of systemic embolism after myocardial infarction. Warfarin is also used as a rodenticide. [PubChem]

Indication

For the treatment of retinal vascular occlusion, pulmonary embolism, cardiomyopathy, atrial fibrillation and flutter, cerebral embolism, transient cerebral ischaemia, arterial embolism and thrombosis.

Pharmacology

Warfarin, a coumarin anticoagulant, is a racemic mixture of two active isomers. It is used in the prevention and treatment of thromboembolic disease including venous thrombosis, thromboembolism, and pulmonary embolism as well as for the prevention of ischemic stroke in patients with atrial fibrillation (AF).

Toxicity

LD₅₀=374 (orally in mice)

Affected Organisms

Biotransformation

Metabolized stereo- and regio-selectively by hepatic microsomal enzymes. S-warfarin is predominantly metabolized by cytochrome P450 (CYP) 2C9 to yield the 6- and 7-hydroxylated metabolites. R-warfarin is metabolized by CYP1A1, 1A2, and 3A4 to yield 6-, 8-, and 10-hydroxylated metabolites. Hydroxylated metabolites may be further conjugated prior to excretion into bile and urine. UGT1A1 appears to be responsible for producing the 6-O-glucuronide of warfarin, with a possibly contribution from UGT1A10. Five UGT1As may be involved in the formation of 7-O-glucuronide warfarin. S-warfarin has higher potency than R-warfarin and genetic polymorphisms in CYP2C9 may dramatically decrease clearance of and increase toxicity of the medication.

Absorption

Rapidly absorbed following oral administration with considerable interindividual variations. Also absorbed percutaneously.

Half Life

R-warfarin t_1/2=37-89 hours; S-warfarin t_1/2=21-43 hours.

Protein Binding

99% bound primarily to albumin

Elimination

The elimination of warfarin is almost entirely by metabolism. Very little warfarin is excreted unchanged in urine. The metabolites are principally excreted into the urine; and to a lesser extent into the bile.

Distribution

* 0.14 L/kg

Clearance

* 0.065 +/- 0.025 mL/min/kg [CYP2C9 Genotype *1/*1]
* 0.041 +/- 0.021 [CYP2C9 Genotype *1/*2 or *1/*3]
* 0.020 +/- 0.011 [CYP2C9 Genotype *2/*2, *2/*3, or *3/*3]

References

External Links