Anticoagulants: Direct factor inhibitors

00:00 / 00:00


Anticoagulants: Direct factor inhibitors


0 / 7 complete


Anticoagulants: Direct factor inhibitors

of complete

Memory Anchors and Partner Content

External References

First Aid









as anticoagulant p. 420

factor Xa inhibitors p. 444


Anticoagulant medications help to prevent thrombi, or blood clots from forming. These medications work by interfering with the normal function of proteins called clotting factors in a chemical process called the coagulation cascade, or secondary hemostasis where hemo refers to blood, and stasis means to halt or stop. While the most common anticoagulants like warfarin and heparin act on multiple coagulation factors, in this video we’re gonna focus on anticoagulants that work on a single coagulation factor; either thrombin or activated factor X.

Now, before we discuss heparin in detail we need to talk about the coagulation cascade which is where heparin exerts its effect. The coagulation cascade starts via two pathways --the extrinsic and intrinsic pathways. The intrinsic pathway starts when circulating factor XII comes into contact with the surface of activated platelets or collagen. Activated factor XII, then activates factor XI, which activates factor IX which activates factor X. Factor X starts the common pathway where it activates factor II, or thrombin, which activates factor I that builds the fibrin mesh. When factor II gets activated it also activates 4 other factors: V, VIII, IX, and XIII. Factor V gets activated and acts as a cofactor for X, factor VIII acts as a cofactor for factor IX, and factor XIII helps factor I, or fibrin, form crosslinks. In the extrinsic pathway, exposed tissue factor activates factor VII, which activates factor X and starts the common pathway.

Now, the most common point of clot regulation is when a coagulation factor called thrombin is produced. Thrombin, or activated factor II, is a very important clotting factor, because it has multiple pro-coagulative functions. Think of thrombin as the accelerator on a car--the pedal that takes secondary hemostasis from 20 miles per hour to 100 miles per hour! First, thrombin binds to receptors on platelets causing them to get activated. Activated platelets change their shape to form tentacle-like arms that allow them to stick to other platelets. Second, thrombin activates two cofactors; factor V used in the common pathway, and factor VIII used in the intrinsic pathway. Third, thrombin proteolytically cleaves fibrinogen or factor I, into fibrin or factor Ia which binds with other fibrin proteins to form a fibrin mesh. And finally, thrombin proteolytically cleaves stabilizing factor or factor XIII into factor XIIIa. Factor XIIIa combines with a calcium ion cofactor to form cross links between the fibrin chains, further reinforcing the fibrin mesh.


  1. "Katzung & Trevor's Pharmacology Examination and Board Review,12th Edition" McGraw-Hill Education / Medical (2018)
  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 (Eds.), Guide to Diagnostic Tests, 7e. McGraw-Hill (2017)
  6. "Use of direct oral anticoagulants in daily practice" Am J Blood Res (2018)
  7. "Manejo de hemorragia asociada a anticoagulantes orales directos: estado actual de las estrategias de reversión" Revista médica de Chile (2019)
  8. "Anticoagulantes orais diretos para o tratamento da trombose venosa profunda: revisão de revisões sistemáticas" Jornal Vascular Brasileiro (2018)

Copyright © 2023 Elsevier, its licensors, and contributors. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

Cookies are used by this site.

USMLE® is a joint program of the Federation of State Medical Boards (FSMB) and the National Board of Medical Examiners (NBME). COMLEX-USA® is a registered trademark of The National Board of Osteopathic Medical Examiners, Inc. NCLEX-RN® is a registered trademark of the National Council of State Boards of Nursing, Inc. Test names and other trademarks are the property of the respective trademark holders. None of the trademark holders are endorsed by nor affiliated with Osmosis or this website.