Variability in the α and β anomer content of commercially available lactose

Lactose, a disaccharide is a ubiquitous excipient in many pharmaceutical formulations which exists in two anomeric forms; either as α- or β-lactose. The anomers have different properties which can affect their application. Nevertheless, batches of lactose products are widely produced by many manufacturers, and is available in many grades. However, the anomeric content of these batches has not been accurately characterized and reported previously. Therefore, the aim of this study was to analyse a set of 19 commercially available samples of lactose using a novel H¹-NMR technique to establish a library showing the anomeric content of a large range of lactose products. The lactose samples were also analysed by DSC. The anomeric content of the α-lactose monohydrate samples were found to vary by more than 10%, which might influence bioavailability from final formulations. The data showed that there is a need to determine and monitor the anomeric content of lactose and this should be a priority to both the manufacturers and the formulators of medicines.