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Topical Delivery of Miconazole-Loaded Microemulsion: Formulation Design and Evaluation
Microemulsions are frequently employed as drug delivery systems to enhance the bioavailability of the incorporated drug via topical, oral and systemic routes. The objective of the present study was to develop a topical microemulsion and evaluate its potential as drug delivery vehicle for a sparingly water soluble antifungal agent, miconazole nitrate. Various combinations of surfactant-cosurfactant (Tween 80 and propylene glycol), castor oil and water were used to construct pseudoternary phase diagrams from which the most efficient emulsifying region was chosen for preparing miconazole nitrate-loaded topical microemulsion. The microemulsion was characterized with respect to globule size, morphology, viscosity, pH and conductivity. The ex vivo release of miconazole from the drug-loaded microemulsion was studied using Franz diffusion apparatus in which the donor compartment was separated from the receptor compartment by a freshly excised hairless rat skin. Results obtained showed that a homogeneous and thermodynamically stable miconazole nitrate-loaded topical microemulsion was successfully prepared with an oil, surfactant and cosurfactant mixture. The ex vivo release study revealed significant drug release from the topical microemulsion, with permeation coefficient values that ranged from 2.5 x 10-6 cm/s to 9.8 x 10-6 cm/s depending on the surfactant-cosurfactant ratio. This study has shown that the problem of poor solubility and bioavailability of miconazole nitrate could be surmounted by incorporating it into lipid-based drug delivery systems such as microemulsions, and that topical microemulsion is a promising tool for percutaneous delivery of miconazole nitrate, thus encouraging further development of this formulation.