Evaluation of Lactose-Based Direct Tableting Agents' Compressibility Behavior Using a Compaction Simulator

A compaction simulator (CS) is a single-punch instrument that records data during the powder compaction process. The aim of the study was to determine the behavior of lactose-based direct tableting agents (DTAs) by CS. The data recorded were used to evaluate the flowability and compressibility of powders. The focus of the study was on comparing the compressibility of StarLac^® [alpha lactose monohydrate (85%) and white maize starch (15%)] and FlowLac^®100 (spray-dried alpha lactose monohydrate) in order to make tablets containing poorly flowable paracetamol.

Two lactose-based DTAs were used. Physical characterization of these powders was done by measuring bulk, tapped, and true densities alongside scanning electron microscopy analysis. Flow properties were then calculated by the angle of repose, Hausner ratio, and Carr's compressibility index. Force, in-die thickness, and punch displacement data produced by the CS were captured during in-die compression. Compressibility was calculated using the Heckel equation.

The physical characterization test results showed no significant difference between the two DTAs. Hardness results revealed that tablet formulations containing FlowLac^® had higher sensitivity to an increase in compression force in comparison with StarLac^®. From the Heckel plots generated by the CS during the compression cycle, yield pressure (P_y) values were calculated for FlowLac^®100 and StarLac^®. The Heckel parameter (P_y) for FlowLac^®100 and StarLac^® was calculated as 87.5 MPa and 85.2 MPa, respectively, during the compaction cycle at 5 kN. These data indicated that both powders are compressible and have brittle behavior.

StarLac® is less brittle, which was shown by its lower sensitivity to compression force. P_y values obtained from the Heckel equation described the plasticity of particles, which gives distinct information on the compressibility of both DTAs in real time during the compaction cycle.