Procoagulants

Procoagulants are substances that promote blood coagulation and facilitate clot formation in response to vascular injury. They act to convert soluble plasma proteins into an insoluble fibrin clot, thereby stopping bleeding and restoring hemostasis. In physiological conditions, coagulation involves a cascade with an intrinsic and extrinsic pathway converging on thrombin generation and fibrin polymerization.

Endogenous procoagulants include tissue factor (the primary initiator of coagulation through factor VIIa), various coagulation factors II (prothrombin), VII, IX, and X, and platelets, which provide a phospholipid surface that supports coagulation reactions. Thrombin (factor IIa) is a central mediator that converts fibrinogen to fibrin and activates additional clotting factors, amplifying the response.

Exogenous or therapeutic procoagulants are used to control bleeding. These include topical thrombin preparations, fibrin sealants, calcium, and concentrates of clotting factors (such as fresh frozen plasma, cryoprecipitate, factor concentrates, or prothrombin complex concentrates). In some settings, these agents are applied to surgical sites to reduce blood loss and support hemostasis.

Clinical relevance: an excess of procoagulant activity can lead to thrombosis, while insufficient activity causes bleeding. Inherited or acquired conditions such as factor V Leiden, prothrombin G20210A, antiphospholipid syndrome, or liver dysfunction can alter procoagulant balance. Laboratory tests such as PT/INR and aPTT assess coagulation status, while thrombin generation assays evaluate overall procoagulant potential. Management aims to preserve hemostasis while minimizing thrombotic risk.