Anticoagulants: Warfarin

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Anticoagulants: Warfarin

Prerequisite basic sciences

Prerequisite basic sciences

Prerequisite basic sciences


Anticoagulants: Warfarin


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Anticoagulants: Warfarin

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Anticoagulant drugs p. 420

warfarin as p. 444


warfarin p. 444

Extrinsic pathway p. 206

warfarin and p. 444

Fresh frozen plasma p. 436

warfarin reversal p. 726

for warfarin toxicity p. 249

Heparin p. 443

warfarin vs p. 444

Hypercoagulability p. 696

warfarin adverse effect p. 444

Necrosis p. 207

warfarin p. 444


warfarin effect on p. 444

Spontaneous abortion

warfarin p. 638

Stroke p. 529

warfarin for p. 444

Teratogens p. 638

warfarin as p. 444

Vitamin K

warfarin reversal p. 726

for warfarin toxicity p. 249, 444

Warfarin p. 444

adverse effects of p. 435

coagulation cascade p. 420

cytochrome P-448 and p. 253

for DVT p. 697

griseofulvin and p. 197

heparin vs p. 444

PT measurement p. 433

reversal of p. 726

teratogenicity p. 638

therapeutic index of p. 235

toxicity treatment p. 249, 436

vitamin K antagonist p. 69


Anticoagulant medications are used to prevent blood clots from forming. These medications work by interfering with the normal function of plasma proteins called coagulation factors, which take part in secondary hemostasis. But let’s focus specifically on the anticoagulant warfarin, which works by preventing the synthesis of coagulation factors II, VII, IX and X, and anticoagulation proteins C and S. Now, to understand the regulation of clot formation we first need to talk briefly about hemostasis-- in which hemo refers to the blood, and stasis means to halt or stop. Hemostasis is divided into two phases: primary and secondary hemostasis.

Primary hemostasis involves the formation of a platelet plug around the site of an injured blood vessel, and secondary hemostasis reinforces the platelet plug with the creation of a protein mesh called fibrin. To get to fibrin, a set of coagulation factors each of which or enzymes need to be activated. These enzymes are activated via a process called proteolysis- which is where a portion of the protein is clipped off. In total, there are twelve coagulation factors numbered factors I-XII, but there’s no factor VI. Most of these factors are produced by liver cells, and it turns out that producing coagulation factors II, VII, IX, and X requires an enzyme that uses vitamin K.

Now, when vitamin K is absorbed from the digestive tract and travels to the liver, it’s in its dietary form and it’s called vitamin K quinone. An enzyme, called quinone reductase, takes electrons from NADPH, and donates them to vitamin K quinone, converting it into the reduced form which is called vitamin K hydroquinone. Then, vitamin K hydroquinone acts as a cofactor by donating its electrons to an enzyme called gamma glutamyl carboxylase, which converts the non-functional forms of coagulation factors II, VII, IX, and X into their functional forms. Gamma glutamyl carboxylase adds a carboxyl group, which is a chemical group made up of one carbon, and two oxygens, onto the end of glutamic acid residues on the proteins.


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  2. "Rang and Dale's Pharmacology" Elsevier (2019)
  3. "Goodman and Gilman's The Pharmacological Basis of Therapeutics, 13th Edition" McGraw-Hill Education / Medical (2017)
  4. "Overview of hemostasis" J.C. Aster, H. Bunn (Eds.), Pathophysiology of Blood Disorders, 2e. McGraw-Hill. (2016)
  5. "Nomograms" D. Nicoll, C. Mark Lu, S.J. McPhee (2017)
  6. "Ischemic Stroke: Risk Stratification, Warfarin Teatment and Outcome Measure" J Atr Fibrillation (2015)
  7. "Critical Issues and Recent Advances in Anticoagulant Therapy: A Review" Neurology India (2019)

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