Solubility Enhancement of Ebastine by Formulating Microemulsion Using D-Optimal Mixture Design: Optimization and Characterization

Ebastine, a histamine H1 antagonist, nonsedating, belonging to BCS class II is used in the treatment of allergic rhinitis and chronic idiopathic urticaria. The current study was intended in augmenting the aqueous solubility and dissolution rate of ebastine, by formulating a microemulsion system using oleic acid, Transcutol^® HP, and Tween^®80 as oily phase, cosurfactant, and surfactant, respectively, by the phase titration method. A custom mixture design with optimality D was used to design the formulation by using the Design Expert^® Software (Version 11; Stat-Ease, Inc., Minneapolis, MN, USA).

Optimization of formulation was performed using the numerical optimization technique, where optimization is based upon the desirability. The optimized formulation was evaluated for transmittance, viscosity, globule size, polydispersity index, zeta potential, drug content, morphological studies, and in vitro studies. The optimized formulation displayed percent cumulative drug release, ranging from 82.9% to 90.6% obtained after dissolution studies and the percent cumulative drug release after diffusion studies ranged from 83.3% to 100%. The in vitro release data were subjected to kinetic treatment. The zero-order and first-order plots were linear and showed the highest values for R², which indicated mixed-order release. The Higuchi plot was linear, indicating diffusion as the mechanism of release. From Peppas plot, it was further confirmed that the release for dissolution studies was anomalous and for diffusion studies it was zero order. Thus, the studies concluded that the microemulsion technique is a very good approach for enhancing the solubility and dissolution rate of the BCS class II drug ebastine.

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