Influence of different types of lactose on powder flow and tablets dissolution

The objective of this study was the evaluation of different types of lactose on the powders flow properties and dissolution of tablets of formulations with captopril and amoxicillin. Data of powders flow rate, compressibility index and dissolution profiles of tablets are presented. The powders flow rate showed higher sensitivity to small changes in their properties, compared to compressibility index. SuperTabs 21AN and 24AN flow at least 20 times faster than Lactopress and lactose NF. Lubrication increases the flow rate, maintaining the observed comparative differences. Dilution of lactoses with 50% captopril or amoxicillin reduces drastically the powder flow, producing also an equalizing effect. The greater flowability of SuperTabs, compared to other types of lactose, practically disappears. Dissolution of lubricated and unlubricated lactose tablets show a much faster dissolution of SuperTab 21AN tablets followed by Lactopress, lactose NF and SuperTab 24AN tablets. Dilution of lactoses with 50% captopril displays a quite smaller dissolution rate with a comparative similar behavior as observed before while dilution with amoxicillin show an equalizing effect of drug dissolution with minor differences between lactoses. The effect of lactose excipients on dissolution is attributed in a greater extent to mechanical properties of their tablets than to differences in solubility and dissolution.