Investigation of the chemical equivalence of the trypanocidal products, Samorin® and Veridium

A procedure for the evaluation of chemical equivalence of proprietary formulations of isometamidium is described. The method combines the analysis of the principal component (isometamidium), HPLC profiling of related substances and determination of the inorganic impurity, ammonium chloride, using a modification of the Berthelot (Indophenol) reaction. Application of these procedures to analyses of commercially available sachets from four different batches of Samorin® and four different batches of Veridium® has demonstrated that there are marked qualitative and quantitative differences between batches from these two sources. Whilst Samorin® samples showed inter-batch consistency of composition, there was considerable inter-batch variation between the samples of Veridium®.