Abstract: A process for preparing thrombin which comprises treating a mixture comprising prothrombin, factor Xa, factor Va, and phospholipids with calcium ions, at a pH of 6.0-7.0 is provided. In particular the pH of 6.0-7.0 may be generated by the addition of the calcium ions or by buffering the preparation to a pH of 6.0-7.0. Thrombin preparations so produced may be subjected to further purification and are particularly stable even when substantially free of exogenous stabilizing agents such as proteins, sugars, polyol and mixtures thereof, and may be subject to freeze-drying and a virus inactivation by heat treatment.

Abstract: A lyophilized fibrinogen is produced which is subjected to a severe terminal virucidal heat treatment in order to inactivate viruses present, while retaining desirable biological properties. In particular the lyophilized fibrinogen has a solubility in water or other aqueous solution to 40 g/l in less than 20 minutes at 20.degree. C., and a clotting time of less than 10 seconds when exposed to at least 200 U/ml thrombin. The product may be heat treated at 80.degree. C. for 72 hours up to 100.degree. C. for 10 hours depending on formulation and water content. In the production process cryoprecipitate is washed with polyethylene glycol solution at 4 to 10.degree. C. and pH 6.8 to 8 at low ionic strength, prior to two-stage freeze drying.