Anhydrous Citric Acid is a tricarboxylic acid found in citrus fruits. Citric acid is used as an excipient in pharmaceutical preparations due to its antioxidant properties. It maintains stability of active ingredients and is used as a preservative. It is also used as an acidulant to control pH and acts as an anticoagulant by chelating calcium in blood. Anhydrous citric acid is a Calculi Dissolution Agent and Anti-coagulant. The mechanism of action of anhydrous citric acid is as an Acidifying Activity and Calcium Chelating Activity. The physiologic effect of anhydrous citric acid is by means of Decreased Coagulation Factor Activity.