Study of thermogravimetric profile of a mixture of diclofenac sodium and para-aminobenzoic acid as a basis for pharmaceutical development

Abstract

In modern conditions, in particular, against the background of an increase in the frequency of traumatic injuries to the organs of vision because of hostilities and the influence of professional factors, the development of new ophthalmic dosage forms is of particular relevance. Combined drugs containing several active pharmaceutical ingredients, in particular diclofenac sodium and para-aminobenzoic acid, are considered promising solutions for the treatment of infectious and inflammatory eye lesions. At the same time, the effectiveness and safety of such combinations directly depend on their physicochemical compatibility, which determines the stability of the finished dosage form. The aim of the study is to investigate the thermal stability and possible physicochemical interactions between diclofenac sodium and para-aminobenzoic acid by derivatographic analysis of individual substances and their mixture in a 1:1 ratio. Materials and methods. The objects of the study were the pharmaceutical substances diclofenac sodium, para-aminobenzoic acid and a model mixture of the specified active pharmaceutical ingredients. Thermogravimetric analysis was carried out on a Shimadzu DTG-60 device in thermogravimetric analysis and differential thermal analysis modes in the temperature range of 17–250°C with a heating rate of 10°C/min in an air atmosphere. Results. In the process of thermogravimetric research, it was established that diclofenac sodium is characterized by high thermal stability. Para-aminobenzoic acid showed three stages of thermal destruction, but analysis of the mixture in a 1:1 ratio did not reveal the appearance of new thermal effects or shifts in the degradation profiles. Conclusions. The results of thermogravimetric analysis indicate the compatibility of diclofenac sodium and para- aminobenzoic acid in terms of thermal characteristics, which confirms the prospects of their simultaneous use.