Evaluation of physical stability of oleogels containing diclofenac diethylamine

Abstract

Oleogels are semisolid systems obtained with an organogelator and a hydrophobic liquid. They have been investigated over the past few years and could play an important role as dermatological bases. Recently, we have developed a formulation containing diclofenac diethylamine (1.16 % w/w) in two oleogel bases of colloidal silicon dioxide (7.0 % w/w) in sesame oil (CSD-SO) and another one of colloidal silicon dioxide (7.5 % w/w) in light liquid paraffin (CSD–LP). The aim of this study was to access their physical stability using different methodologies. The gels were stored at different temperatures (20 - 50 ^oC) over a period of six months. Appearance and textural properties were assessed each month. An accelerated test was also performed where the temperature changed between 4 and 40 ^oC every 24 h, during 7 days. Rheological tests were also carried out as they could provide useful elements to predict stability. The textural properties of both gels were influenced by temperature. The decrease of the textural parameters, observed after storage at 40 ^oC and in the cycling test, was more significant in case of CSDLP gels. The heating/cooling cycle test provided useful information in a short period of time. The gels were quite stable at 20 oC, being the CSD-SO gel the most stable.