NMR spectroscopy and surface tension measurements applied to the study of self-association of casopitant mesylate, a novel NK1 antagonist.

The aggregation behaviour of casopitant mesylate, a new NK1 antagonist drug, was investigated by means of NMR spectroscopy and surface tension measurements. The critical micelle concentration (CMC) in glycine buffer at pH 3.5 was determined by analyzing the 1H NMR chemical shifts variation and the surface tension in function of the concentration in a series of solutions. The temperature dependence of the CMC was also evaluated by NMR spectroscopy as well as the thermodynamic parameters contributing to the aggregation discussed. Surface tension measurements were conducted as well in the formulation conditions, e.g. in the presence of sodium chloride.