Stability and self-nanoemulsification efficiency of ramipril nanoemulsion containing labrasol and plurol oleique

The aim of the present investigations was to evaluate the capacity of a combination of Labrasol and Plurol oleique as surfactant and cosurfactant on self-nanoemulsification efficiency of ramipril nanoemulsion. Sefsol-218, Labrasol, Plurol oleique, and standard buffer solution (pH 5.0) were selected as oil phase, surfactant, cosurfactant, and aqueous phase, respectively. Nanoemulsion formulations of ramipril were developed by a spontaneous emulsification method. Pseudoternary phase diagrams were constructed to identify nanoemulsion zones of ramipril. Selected formulations were evaluated in terms of thermodynamic stability tests using centrifugation, heating–cooling cycles, and freeze–thaw stress test. Some formulations were found stable and other formulations were unstable upon thermodynamic stability tests. Thermodynamically stable formulations were taken for self-nanoemulsification efficiency test. All the selected formulations passed self-nanoemulsification test in grade E only but not in grades A and B. Because none of the formulations passed the self-nanoemulsification efficiency test in grades A and B, it was concluded that a combination of Labrasol and Plurol is not suitable as surfactant and cosurfactant, respectively, for oral or self-nanoemulsifying drug delivery system of ramipril.