Heparin

From ArticleWorld

Heparin is a chemical that is commonly used as an anticoagulant. It is composed of a sulfated glycosaminoglycan. Its applications include as an injectable coagulant as well as a chemical to form anticoagulant coatings on the inner surfaces of test tubes and dialysis machines. It is derived mainly from the tissues of other animals. This drug is one of the oldest drugs still in use and was first isolated from liver cells.

This drug is used in the prevention of clot formation and the extension of existing clots within the blood. It does not break down clots that have already formed but halts the natural clot forming and breaking down mechanisms. It is used in the treatment of atrial fibrillation, acute coronary syndrome and pulmonary embolisms.

Structure

It is a polymer which is a member of the glycosaminoglycan group of carbohydrates. One of the most common heparin disaccharide units is made up of an 2-O-sulfated iduronic acid and 6-O-sulfated, N-sulfated glucosamine, IdoA(2S)-GlcNS(6S). This compound is found in beef lung as well as in porcine intestinal mucosa. It accounts for between 75-85%of the heparin in these tissues. Some rare heparin disaccharides include a 3-O-sulfated glucosamine (GlcNS(3S,6S) or a free amine group (GlcNH3+). The form that is used in heparin administration is mainly the heparin salt which is formed when the ester and amide sulfur groups are deprotonated and attract positively charged ions.

Mechanism of action

Heparin first binds itself to the enzyme inhibitor of clotting and causes a change resulting in it being available to reaction as its active sites are exposed. This increases the rate at which the thrombin is inactivated and other proteases involved in clotting as well. The inhibition of thrombin also requires that the thrombin bind to the heparin polymer. Thus it is a three-fold structure combining the thrombin, enzyme inhibitor and heparin that inactivates clotting.