Name:  Dextran

Synonyms:  Mucrose; Glucose polymer

Molecular Structure:  

Molecular Formula:  [C₆H₁₀O₅]_n

CAS Number:  9004-54-0

EINECS:  232-677-5

 

Dextran is a complex, branched glucan composed of chains of varying lengths (from 10 to 150 kilodaltons). Dextran is used medicinally as an antithrombotic (anti-platelet), to reduce blood viscosity, and as a volume expander in anemia. The straight chain consists of ¦Á-1,6 glycosidic linkages between glucose molecules, while branches begin from ¦Á-1,4 linkages (and in some cases, ¦Á-1,2 and ¦Á-1,3 linkages as well). Dextran is synthesized from sucrose by certain lactic-acid bacteria, the best-known being Leuconostoc mesenteroides and Streptococcus mutans. Dental plaque is rich in dextrans. Dextran is also formed by the lactic acid bacterium Lactobacillus brevis to create the crystals of tibicos, or water kefir fermented beverage which supposedly has some health benefits.

Dextran is used commonly by microsurgeons to decrease vascular thrombosis. The antithrombotic effect of dextran is mediated through its binding of erythrocytes, platelets, and vascular endothelium, increasing their electronegativity and thus reducing erythrocyte aggregation and platelet adhesiveness. Dextrans also reduce factor VIII-Ag Von Willebrand factor, thereby decreasing platelet function. Clots formed after administration of dextrans are more easily lysed due to an altered thrombus structure. By inhibiting ¦Á-2 antiplasmin, dextran serves as a plasminogen activator and therefore possesses thrombolytic features.

Larger dextrans, which do not pass out of the vessels, are potent osmotic agents, and thus have been used urgently to treat hypovolemia. The hemodilution caused by volume expansion with dextran use improves blood flow, thus further improving patency of microanastomoses and reducing thrombosis. Still, no difference has been detected in antithrombotic effectiveness in comparison of intraarterial and intravenous administration of dextran.

Dextrans are available in multiple molecular weights ranging from 10,000 Da to 150,000 Da. The larger dextrans are excreted poorly from the kidney and therefore remain in the blood for as long as weeks until they are metabolized. Subsequently, they have prolonged antithrombotic and colloidal effects. In this family, dextran-40 (MW: 40,000 Da), has been the most popular member for anticoagulation therapy. Close to 70% of dextran-40 is excreted in urine within the first 24 hours after intravenous infusion while the remaining 30% will be retained for several more days.

Dextran is used in some eye drops as a lubricant, and in certain intravenous fluids to solubilise other factors, e.g. iron (=iron dextran). Dextran in intravenous solution provides an osmotically neutral fluid that once in the body is digested by cells into glucose and free water. Dextran is occasionally used to replace lost blood in emergency situations, when replacement blood is not available, but must be used with caution as it does not provide necessary electrolytes and can cause hyponatremia or other electrolyte disturbances. Dextran also increases blood sugar levels.