Variability of Uniformity of Weight Test as an Indicator of the Amount of Active Ingredient in Tablets

Abstract

Fifty-four samples, embracing five drugs sold as compressed tablets, were obtained. Individual tablet weights were determined and individual chemical assays were carried out on 10 tablets from each sample. There was little or no relationship between the amount of active ingredient and tablet weight for promazine tablets in which the active ingredient formed a small proportion (15–23 per cent) of tablet weight, but this relationship was high for tolbutamide tablets in which the active ingredient formed a large proportion (73–90 per cent) of tablet weight. This observation suggests that the uniformity of weight test may sometimes be usefully employed instead of individual tablet chemical assays when the proportion of active ingredient in the tablets is high and that the emphasis in developing direct measures of content uniformity should be placed on preparations containing small proportions of active ingredient. The present data do not confirm the observation of Mos-kalyk et al. (1961) that "Greater deviations ‘in active ingredient' were found to occur in lighter weight tablets" within preparations.