12.3 Pharmacokinetics
Hetastarch molecules below 50,000 molecular weight are rapidly eliminated by renal excretion. A single dose of approximately 500 mL of 6% Hetastarch in 0.9% Sodium Chloride Injection (approximately 30 g) results in elimination in the urine of approximately 33% of the dose within 24 hours. This is a variable process but generally results in an intravascular hetastarch concentration of less than 10% of the total dose injected by two weeks. A study of the biliary excretion of 6% Hetastarch in 0.9% Sodium Chloride Injection in 10 healthy males accounted for less than 1% of the dose over a 14 day period. The hydroxyethyl group is not cleaved by the body but remains intact and attached to glucose units when excreted. Significant quantities of glucose are not produced as hydroxyethylation prevents complete metabolism of the smaller polymers.
The addition of hetastarch to whole blood increases the erythrocyte sedimentation rate. Therefore, 6% Hetastarch in 0.9% Sodium Chloride Injection is used to improve the efficiency of granulocyte collection by centrifugal means.