Drugs Acting on Blood Coagulation: Anticoagulants and Fibrinolytics

1. Blood Coagulation Process:

• When bleeding occurs, the body responds by:

• Vasoconstriction: Reducing blood flow.

• Platelet Plug Formation: Platelets adhere to the wound, forming a temporary seal.

• Fibrin Formation: Fibrin strands connect to the platelet plug, creating a stable blood clot.

2. Drugs Affecting Blood Coagulation:

• Coagulants:

• Vitamin K (K-drugs):

• Mechanism: Vitamin K activates coagulation factors II, VII, IX, and X.

• Indications: Premature infants, miscarriage, frequent diarrhea, individuals with bile acid-related diseases.

• Route of administration: Oral, intravenous injection.

• Antiplatelet Drugs:

• Mechanism: Inhibit platelet activation, preventing platelet plug formation.

• Types:

• Thromboxane A2 inhibitors: Aspirin.

• ADP inhibitors: Clopidogrel, ticlopidine, prasugrel, ticagrelor.

• GP IIb/IIIa inhibitors: Abciximab (used in emergencies), eptifibatide, tirofiban.

• PDE enhancers: Dipyridamole.

• Vasodilator in the occluded area: Cilostazol.

• ADRs:

• Aspirin: Gastric ulceration, diarrhea, elevated liver enzymes.

• Anticoagulants:

• Mechanism: Inhibit fibrin formation, reducing blood coagulation ability.

• Types:

• Thrombin IIa inhibitors:

• Indirect: Heparin (intravenous injection, subcutaneous injection), fondaparinux (intravenous injection, subcutaneous injection).

• Direct: Hirudin (injection), dabigatran (oral).

• Xa inhibitors:

• Indirect: Low-dose heparin, idaparinux, fondaparinux (intravenous injection, subcutaneous injection).

• Direct: Rivaroxaban, apixaban, edoxaban (oral).

• Vitamin K antagonist anticoagulants: Warfarin, dicumarol.

• ADRs:

• Heparin: Thrombocytopenia, osteoporosis, bleeding.

• Warfarin: Bleeding, drug interactions, contraindicated in pregnancy, individuals using artificial heart valves.

• Principles of Anticoagulation: Cutting a coagulation factor or removing calcium (outside the body).

• Fibrinolytics:

• Mechanism: Dissolve pre-formed blood clots.

• Types:

• Non-selective fibrinolytic agents: Streptokinase, urokinase.

• Non-heterologous fibrinolytic agents: Urokinase.

• Selective fibrinolytic agents: Alteplase, reteplase, tenecteplase.

• ADRs:

• Streptokinase: Heterologous shock, widespread bleeding.

3. Summary:

Drugs acting on the blood coagulation process come in many types, each with a different mechanism of action, used in different pathological conditions. The use of these drugs must be prescribed by a specialist to ensure safety and effectiveness.