The resistance to compression index as a parameter to evaluate the efficacy of lubricants in pharmaceutical tabletting

A new technique is introduced in this investigation to measure a resistance to compression index (RCI) for granulations and direct compression powder blends with increasing concentration (C) of lubricants as parameter of their efficacy. RCI, denoted as kC, was determined from the slope of a developed expression: % ∆ L = Ac exp. -kc C, where % ∆ L is the percentage reduction in the powder column due to tabletting. The constant A stands for the percentage reduction in the control (unlubricated) powder column due to tabletting. Magnesium stearate (MS) gave the smallest kc value and was therefore indicated as a reference lubricant. The percentage relative lubrication efficacy (%RLE) of any tested lubricating material was calculated. It was in the case of granulation 77% with stearic acid, 32% with sodium lauryl sulfate and 25% with talc while in direct compression mixes it was 44% with stearic acid, 57% with sodium lauryl sulfate and 41% with talc, respectively. RCI or kc values were found to be correlated to the hardness and dissolution of the tablets.