» Heparin Calcium is the calcium salt of sulfated glycosaminoglycans present as a mixture of heterogeneous molecules of mixed mucopolysaccharide nature varying in molecular weights. It is present in mammalian tissues and is usually obtained from the intestinal mucosa or other suitable tissues of domestic mammals used for food by humans. The sourcing of heparin material must be specified in compliance with applicable regulatory requirements. The manufacturing process must be validated to demonstrate clearance and inactivation of relevant infectious and adventitious agents (e.g., viruses, TSE agents). See Viral Safety Evaluation of Biotechnology Products Derived From Cell Lines of Human or Animal Origin 1050 for general guidance on viral safety evaluation. (RB 18-Jun-2008) It is purified to retain a combination of activities against different fractions of the blood clotting sequence. It is composed of polymers of alternating derivatives of - (RB 18-Jun-2008) d-glucosamine (N-sulfated, O-sulfated, or N-acetylated) and uronic acid (- (RB 18-Jun-2008) l-iduronic acid or - (RB 18-Jun-2008) d-glucuronic acid) joined by glycosidic linkages. The component activities of the mixture are in ratios corresponding to those shown by the USP Heparin Sodium Reference Standard. Some of these components have the property of prolonging the clotting time of blood. This occurs through the formation of a complex of each component with the plasma proteins antithrombin III and heparin cofactor II to potentiate the inactivation of thrombin. Other coagulation proteases in the clotting sequence, such as activated factor X (factor Xa), are also inhibited. The potency of Heparin Calcium, calculated on the dried basis, is not less than 140 USP Heparin Units in each mg, and not less than 90.0 percent and not more than 110.0 percent of the potency stated on the label. Heparin Calcium is essentially free from sodium.