An emulsion is a biphasic, metastable coarse dispersion of two immiscible materials, usually liquids (typically oil and water), that produces a semisolid. Common emulsions can be oil suspended in water or aqueous phase (o/w) or water suspended in oil (w/o). In addition to these two types, a relatively complex emulsion, called multiple emulsions can also be formulated.

Pharmaceutical emulsions are used for the administration of nutrients, drugs, and diagnostic agents. Topical creams and lotions are popular forms of emulsions for external use. By considering the particle size, pharmaceutical emulsions can be classified into four types: macroemulsions, miniemulsions, microemulsions, and nanoemulsions.

Among them, the use of microemulsions as drug delivery vehicles has been an exciting and attractive research field because of its many potentials and extraordinary benefits. Nanoemulsion has become one of the greatest and advantageous dosage forms with the application of nanotechnology in pharmaceutical formulations.

※ Microemulsion
A microemulsion is an emulsion in which the dispersed phase is in the form of very small droplets, usually produced and maintained with the aid of surfactants, ranging in diameter from 50 to 500 angstroms. In the pharmaceutical field, microemulsions are considered to be one of the most suitable forms of drug delivery because they are based on the adsorption of nanodroplets which can form reservoirs and limit drainage or removal of drugs.

Microemulsion formulations offer several benefits over conventional oral formulation for oral administration including increased absorption, improved clinical potency, and decreased drug toxicity. Therefore, microemulsion has been reported to be the ideal delivery of drugs such as steroids, hormones, diuretics and antibiotics.

※ Nanoemulsion
The world of biomedical science has recently changed significantly with the development of nanotechnology which has enabled scientists to think more precisely in designing better therapies. Nanotechnology is the science of dealing with nano-sized particles. The use of nanotechnology in pharmaceutical sciences has emerged in the past few years and has aroused great interest. Nanoemulsions are one of the pharmaceuticals currently being used or in the process of development by using nanoparticles.

The use of nanoemulsion spreads from antibiotic therapy, atherosclerosis treatment, transdermal drug delivery and ophthalmic application to as far as cancer therapy, vaccine delivery, etc. For example, nanoemulsions can be modified using ligands of different natures to target components present on the surface of tumor cells or to escape multidrug resistance (MDR) mechanisms. A large number of studies have shown that nanoemulsions can be effectively taken by tumor cells to reduce tumor growth, eliminate toxicity to healthy cells, and reduce the migration of cancer cells to other organs.

The successful therapeutic effect of micro or nano emulsified drugs is closely related to the self-emulsifying drug delivery system (SEDDS). The use of SEDDS has significant potential to improve oral bioavailability of drugs with poor aqueous solubility. Oral bioavailability of hydrophobic drugs can be improved using SEDDS, and appears most promising. Their dispersion in gastrointestinal (GI) fluid after administration forms micro or nano emulsified drug which gets easily absorbed through lymphatic pathways bypassing the hepatic first pass metabolism. With future development of this technology, SEDDSs will continue to enable novel applications in drug delivery and solve problems associated with the delivery of poorly soluble drugs.

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A big fan of biotechnology!