Segregation of vibrated powder mixes containing different concentrations of fine potassium chloride and tablet excipients.

The effect of different drug/excipient concentrations on the segregation tendency of three ordered powder mixes was studied. In addition, the influence of vibration frequency on the segregation intensity and mechanisms of segregation was also studied. Differences in content uniformity of the powders were measured by comparing samples from regions at different depths between the upper exposed powder surface and the base of the cylindrical container. Ordered mixes containing recrystallized lactose excipient and fine-particle potassium chloride as a model drug were found to be least susceptible to segregation at most vibration conditions for all potassium chloride concentrations. Dipac excipient/potassium chloride particles were most susceptible to segregation under all test conditions. In general, segregation intensity was most marked in conditions where high potassium chloride concentrations, above 2% w/w, were subjected to low-frequency vibration, below 100 Hz. Segregation mechanisms were considered to be mainly dependent on vibration conditions, although carrier excipient type markedly modified mechanisms and influenced segregation intensity.