Stability Study of Sodium Risedronate Microemulsion in different Physical and Thermal ways

Microemulsions are described as dispersing of two unpaired liquids together into a single transparent, clear, thermodynamically stable liquid with small nanometer dimensions ranging from 10-100 nm1. The microemulsion has high stability and long shelf life. Phase separation or creaming or sedimentation is not expected within it, and this distinguishes it from other emulsions whose stability is poor and the shelf life is short1. In this paper, we amed to verify the stability of the two medicinal microemulsion formulations of Sodium Risedronate through physical (centrifugation) and thermal stability tests (thermal cycles, constant temperatures for a month), with a focus on comparing some characteristics of microemulsions (physical appearance, Refraction Index, droplet dimensions, etc.) before and after the stability study to investigate any change that occurred. The only change was in the thermal tests with droplet dimensions for the formula with higher cosolvent concentration (1/2) (Tween 80/glycerin) without significant changes for the formula with higher surfactant content (2/1).