Fibrinogen is the soluble constituent of plasma and when thrombin is added to it, fibrinogen is converted to fibrin. After separation from plasma by fractionation, the precipitate is collected by centrifugation, dissolved in citrate saline and freeze-dried. The air in the containers is displaced by nitrogen.

The citrate prevents spontaneous clotting when the material is reconstituted. Fibrinogen dissolves slowly. However, like many of the protein solutions, it froths badly if shaken and the solid-stabilized foam is very slow to disperse. Hence, agitation should be done in a gentle manner. The solution should be used immediately or within three hours of preparation.

Uses: Fibrinogen is administered alone to treat fibrinogen deficiency, but more often it is used in conjunction with thrombin.