Uniformity of weight test: a non-destructive test compared to the European Pharmacopoeia test

The test for uniformity of weight as stipulated in the European Pharmacopoeia (Ph. Eur) is a complicated and time consuming method. The aim of the present project was to prove, that a new method developed in the Pharmacy Department of the University Hospital of Heidelberg is in principle equivalent to the Ph. Eur. method. Six lots of capsules were produced with a hand operated capsule filling machine. They were filled with mannitol and Aerosil®. Three lots of capsules contained 0.5% Aerosil and the other three lots contained 5% Aerosil. Before filling the capsules, the lot specific empty capsule weight was defined in order to determine the real weight of contents. According to the Ph. Eur. method and our method the filling weight was calculated in two different ways. The results of both methods were compared always in relation to the real weight of contents of the capsules. The results suggested that the average filling weight of the Ph. Eur. method could never be well-defined because there is always substance left in the capsules when they are emptied in order to determine the empty weight. These findings demonstrated that our approach can be considered at least as good as the European Pharmacopoeia method. Furthermore the average filling weight of our method was more accurate which raises the question if the Ph. Eur. should be revised in this regard.