Measurement and control of quality determining properties of clinical dextrans

For plasma substitutes a main requirement is that they give plasma volume expansion. For dextran this property has been shown to be molecular weight dependent. The magnitude and duration of the volume effect, and the magnitude and rate of the excretion of dextrans have been carefully studied with regard to the correlation with molecular weight. Other clinically important effects like flow promotion and disaggregation of erythrocytes also have shown correlation with molecular weight. The measurement and control of the molecular weight distribution (MWD) of clinical dextrans thus is an important quality measure. The tolerance limits must be so set that a clinically relevant discriminating effect is obtained. In most of the current official monographs methods give only average figures of the MWDs or of broad fractions of the MWDs. In some cases these figures are not even molecular weight figures but viscosity figures. In the 1960's gel permeation chromatography (GPC) methods were developed for quality control of dextran. These methods are now suggested and considered for some pharmacopoeias, and are already introduced into one, namely the Nordic Pharmacopoeia. With these methods information of the total MWD is obtained. The proportion of dextran in a desirable molecular weight range can be directly seen, and presence of dextran with undesirable molecular weight can be revealed.