Abstract:

Solubilization capacity and structural transformations in nonionic microemulsions characterized by a large continuous isotropic region forming dilutable self-assembled nanodroplets contg. solubilized carbamazepine, were studied along diln. lines 73 and 82 (70 and 80% surfactant and 30 and 20% of oil phase, resp.). The prepns. were based on pharma-grade ingredients, water, R-(+)-limonene, ethanol, propylene glycol, and Tween 60. Solubilization capacity (SC) of the drug was dependent on the microstructure of the microemulsion and on the surfactant-to-oil phase wt. ratio. The SC in the conc. (reversed micelles) was 15 times higher than its soly. in the oil. Transition of the W/O microemulsion to a bicontinuous phase and to O/W droplets were identified by elec. cond., viscosity, SAXS, and SD-NMR measurements. Once the system is dild. to 90% aq. phase, the SC is 10 and 16-fold higher, along diln. lines 73 and 82, resp., than in pure water. Being solubilized, carbamazepine serves as a cosurfactant therefore it affects the curvatures of the microstructures and consequently the boundaries of the structural regions and the transition points between the different phases. Dilutable microemulsions are promising new carbamazepine vehicles for oral intake. [on SciFinder(R)]