Characterization of melt extruded and conventional Isoptin formulations using Raman chemical imaging and chemometrics.

Isoptin SR-E (Meltrex(®)) extruded tablets were assumed in a recent paper to be prepared with a composition different from a conventional (Isoptin SR) formulation. This study reveals, however, using Raman mapping and chemometric evaluation, that in fact the same composition, comprising Na alginate as polymer matrix, is used in both products. It means that only the difference in the manufacturing technology causes the reported sustained release of verapamil hydrochloride even in ethanol containing dissolution media. The products are compared based on the obtained Raman chemical images, which allowed concluding in a new structure-based explanation for the differences in the dissolution profiles in the presence of ethanol. It is also shown that extrusion technology influences the dissolution profile effectively, even in the cases when solid solution is formed only partially.