Contemporary Strategies in Emulsified Drug Delivery Systems: A Retrospective Overview

Abstract

Oral bioavailability of drugs can be augmented by self-emulsifying systems. Different self-emulsifying systems such as self-emulsifying drug delivery systems (SEDDS), self-microemulsifying drug delivery systems (SMEDDS), and self-nanoemulsifying drug delivery systems (SNEDDS) offerstrategic drug delivery systems to improve the solubility, permeability and bioavailability of both hydrophilic andhydrophobic drug moieties. The success of commercial formulations such as Sandimmune Neoral brand of cyclosporine A andFortovase of Saquinavir escalated interest in lipid based formulations. Self micro-emulsifying drug delivery systems (SMEDDS) are isotropic mixtures of lipids (oils), surfactant and co-surfactant with unique property of producing oil-in-water (o/w) microemulsion upon gentle agitation. Current research is focused on self double emulsifying drug delivery systems (SDEDDS) for effective administration of hydrophilic active moieties, proteins and peptide drugs. The SDEDDS comprises double emulsionsof larger oil droplets incorporating an aqueous internal phase existing in a dispersed phase in an aqueous dispersion medium. The solid forms of lipid based drug delivery systems have been developed to overcome their stability problems. This article provides an overview on novel emulsions, physico-chemical factors of SMEDDS, excipients used for self emulsification, aspects on formulation and the mechanism of drug transport through SDEDDS. This review specially emphasizes on the techniques which are employed in converting the liquid/semi solid self-microemulsifying systems into solid-self microemulsifying formulations. Encapsulation process, spray drying, adsorption onto inert vehicles, melt granulation and melt extrusion techniques were evidenced retrospectively in this article. Solid SEDDS are suitable for lipophilic drugs while solid SDEDDS are most suited for hydrophilic moieties.