Blood coagulation enhancers

Mechanism of action and vitamin K preparations

Vitamin K plays a key role in the hemostatic system. It acts as a coenzyme (in the hydroquinone form) in the $\gamma$-carboxylation of glutamic acid residues. This is essential for the synthesis of functional procoagulants (factors II, VII, IX, X), natural anticoagulants (proteins C and S) in the liver, as well as the bone tissue protein osteocalcin.

These reactions yield $\gamma$-carboxyglutamic acids capable of binding calcium ions. Without calcium, the factors cannot anchor to platelet and endothelial cell membrane phospholipids, the activation cascade is interrupted, and bleeding occurs. Hypovitaminosis leads to the synthesis of acarboxy proteins — inactive factor precursors.

Several forms of the vitamin are distinguished:

• Natural (fat-soluble): vitamin K1 (phylloquinone of plant origin) and K2 (menaquinones synthesized by gut microflora).
• Synthetic: phytomenadione (K1 analogue) and menadione (vitamin K3). The latter is a water-soluble provitamin. In medicine, its dosage form vikasol (menadione sodium bisulfite) is used.

The drugs are prescribed for hemorrhagic disease of the newborn, indirect anticoagulant overdose, and malabsorption syndrome. Their use requires caution: allergic reactions are possible, intravenous administration carries a high risk of anaphylactoid reactions, and in newborns, vikasol can trigger hemolytic anemia and hyperbilirubinemia.

Blood coagulation factor preparations

These form the basis of replacement therapy for hereditary or acquired deficiencies. Since endogenous factors have a short half-life, patients require regular infusions.

1. Factor VIII (Haemofil M, Immunate). Derived from plasma with double viral inactivation. Used for hemophilia A and von Willebrand disease. An alternative is cryoprecipitate, a plasma protein concentrate containing factor VIII, von Willebrand factor, and fibrinogen.
2. Factor IX (Agemfil B, Octanyn, Immunine). A purified plasma fraction for treating hemophilia B and reversing vitamin K antagonist overdose.
3. Factor VII (eptacog alfa activated / NovoSeven). A recombinant product effective in deficiencies of factors VII, V, II, IX, and X.

The main issue with donor plasma products is the risk of transmitting blood-borne infections (HIV, hepatitis). To address this, modern practice increasingly shifts toward recombinant products.

For mild coagulopathies (e.g., mild hemophilia A), an alternative exists — desmopressin. This synthetic analogue of arginine vasopressin stimulates the release of von Willebrand factor from the endothelium, which secondarily increases factor VIII activity.

Local and herbal hemostatics

Topical agents are used to stop capillary bleeding and hemorrhage from parenchymal organs. Thrombin (isolated from donor plasma) and hemostatic sponges (based on collagen or gelatin) form a reliable mechanical matrix upon which a blood clot rapidly develops.

Herbal hemostatics are widely used in the treatment of uterine, pulmonary, renal, and intestinal bleeding. The pharmacological effect is exerted by extracts, infusions, and tinctures from nettle leaves, yarrow herb, water pepper (smartweed) and pale persicaria, as well as arnica flowers and Lagochilus inebrians. These agents are administered both orally and topically.

Class and exam questions

What else to study on this topic

• Biochemical cascade of $\gamma$-carboxylation of glutamic acid residues
• Pathogenesis of hemorrhagic disease of the newborn
• Comparative profile of plasma-derived and recombinant clotting factors
• Mechanisms of action of local hemostatic sponges and thrombin
• Pharmacokinetics of fat-soluble and water-soluble forms of vitamin K

Other topics in the section "Drugs affecting hemostasis and thrombosis"

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.