Quality evaluation of generic mebendazole by DRIFT spectrometry and ANN spectral modelling

Mebendazole, a broad spectrum anthelmintic drug, exists in three polymorphic forms (A, B and C) with differing solubilities and rates of dissolution. The order of solubility is B>C>A. with polymorph B, seven times more soluble than A, while the order of stability is A>C>B. The fact that different therapeutic outcomes have been attributed to the different polymorphs supports the fact that low solubility and rate of dissolution are important factors to consider. The objective of this study was to develop a simple non-destructive method to test the crystal purity of the mebendazole raw material (bulk drug), and thus ensure that the pharmaceutically favoured polymorph C is present in both tablet and liquid dosage forms. A Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectrometry method was developed for detection of the unfavourable polymorph A (as impurity) in the raw material samples. The results obtained showed that the DRIFT spectrometry method combined with the artificial neural network (ANN) modelling can be successfully used not only to distinguish between the polymorphs but also to quantify the crystal purity (