Action and Clinical Pharmacology
NIRHES contains Hydroxyethyl starch in a colloidal solution. which expands plasma volume when administered intravenously. The low molecular substitution (0.4) is the main pharmacological determinant for the beneficial effects of NIRHES on pharmacokinetics, intravascular volume and haemodilution. The pharmacokinetic profile of Hydroxyethyl Starch is complex and largely dependent on its molar substitution as well as its molecular weight. When administered intravenously molecules smaller than the renal threshold (60,000 – 70,000 Daltons) are readily and rapidly excreted in the urine, while molecules with higher weights are metabolized by plasma alpha-amylase prior to excretion via renal route following intravenous administration of 500ml Hydroxyethyl starch results in elimination in the urine of approximately 62% of the dose within 72 hrs.