The Influence of Microstructure on Celecoxib Release from a Pharmaceutically Applicable System: Mygliol 812^®/Labrasol^®/Plurol Oleique^®/Water Mixtures

Alenka Zvonar,¹ Branka Rozman,¹ Marija Bešter Rogač² and Mirjana Gašperlin^1,*

¹ University of Ljubljana, Faculty of Pharmacy, Aškerčeva 7, 1000 Ljubljana, Slovenia
² University of Ljubljana, Faculty of Chemistry and Chemical Technology, Aškerčeva 5, 1000 Ljubljana, Slovenia
* Corresponding author: E-mail: mirjana.gasperlin@ffa.uni-lj.si

Abstract
Structural transformations were investigated in unloaded and celecoxib-loaded microemulsions on a dilution line containing, initially, 12 wt. % of Mygliol 812^® and 88 wt. % of the surfactant (Labrasol^®)/co-surfactant (Plurol Oleique^®), 4:1 wt. % mixture. Electrical conductivity, viscosity, surface tension and density measurements revealed that two structural transitions take place along the dilution line studied. At ~27 wt. % of water the oil-continuous (w/o) system converted to a bicontinuous microemulsion and a transition to a water-continuous (o/w) microemulsion followed at ~45 wt. % of water. After incorporation of celecoxib at 1 wt. % concentration the microemulsion remained stable and no change in its microstructure was observed. Celecoxib release was then measured for each type of microemulsion. It was shown to be influenced by the microstructure and solubilization capacity of the system, and can, to a certain extent, be predicted. Stability testing of celecoxib-loaded microemulsions revealed that they are stable over 90 days storage at 40 °C.

Keywords: Microemulsions, microstructure, drug release, stability, celecoxib, solubilization