Heparin sodium API (active pharmaceutical ingredient) is a type of anticoagulant medication used to prevent and treat blood clots in the body. The mechanism of action of heparin sodium API is based on its interactions with specific clotting factors in the blood to prevent the formation of fibrin, which is a protein that forms the basis of blood clots.

　　Heparin sodium API works by binding to and activating a natural anticoagulant called antithrombin III (ATIII). ATIII is an enzyme that inhibits the activity of coagulation enzymes such as thrombin, which is a critical enzyme in the coagulation cascade. By activating ATIII, heparin sodium API indirectly inhibits thrombin's activity, thus preventing the conversion of fibrinogen to fibrin, which is necessary for blood clotting.

　　In addition to its indirect effect on thrombin, heparin sodium API can also directly inhibit the activity of another clotting enzyme called factor Xa. Factor Xa is a key enzyme in the clotting pathway, and inhibiting its activity hinders the formation of blood clots.

　　Heparin sodium API is typically administered through injection due to its low oral bio-availability. Once injected into the body, it circulates in the bloodstream, exerting its anticoagulant effects. Its duration of action is largely dependent on the dose and method of administration.

　　It is important to note that while heparin sodium API is highly effective at preventing and treating blood clots, it carries a risk of bleeding, which may be increased in certain patient populations, such as those with renal failure or liver disease. Therefore, careful monitoring and dose adjustment may be necessary for certain patient populations to avoid associated risks.

　　In conclusion, heparin sodium API works by activating antithrombin III and inhibiting the activity of thrombin and factor Xa in the coagulation cascade, which prevents the formation of fibrin and ultimately prevents blood clotting. Its effects can be potent, but proper medical guidance and monitoring are necessary to minimize potential risks and ensure optimal treatment effectiveness.