MICROEMULSION AND ITS APPLICATIONS NOVEL APPROACH TOWARDS THE DRUG DELIVERY
Suchita.G.Waghmare*, Rasika R.Nikhade, Mahesh A.Hadke
ABSTRACT
A microemulsion is a system of water, oil and an amphiphiles which is
a single optically isotropic and thermodynamically stable liquid
solution. Microemulsions can be considered as small-scale versions of
emulsions, i.e., droplet type dispersions either of oil-in-water (o/w) or
of water-in-oil (w/o), with a size range in the order of 5−50 nm in drop
radius. Microemulsion formation is dependent on surfactant type and
structure. The microemulsion formulations consist of one or more
surfactants in combination with co-surfactant and drug dissolved in oil.
If the surfactant is ionic and contains a single hydrocarbon chain
microemulsion are only formed if a co-surfactant and/or electrolyte are
also present. With double chain ionic and some non-ionic surfactants a
co-surfactant is not necessary. Oils form a distinct core in the interior of the surfactant
aggregate, resulting in enhanced solubilizing capacity of the oils with improved drug loading
capacities of the microemulsion. Microemulsions are optically isotropic and
thermodynamically stable liquid solutions of oil, water and amphiphile. Microemulsions are
readily distinguished from normal emulsions by their transparency, low viscosity and more
fundamentally their thermodynamic stability. It is well established that medium chain fatty
acids influence tight junctions of the epithelial cells, and long chain fatty acids stimulate the
lipoprotein synthesis and subsequent lymphatic absorption. Microemulsions are shown to be
effective dermal delivery mechanism for several active ingredients for pharmaceutical and
cosmetic applications. Topical microemulsion allows rapid penetration of active molecules
due to the large surface area of the internal phase, and their components reduce the barrier
property of stratum corneum. Microemulsions thereby enhance dermal absorption compared
with conventional formulations and are therefore a promising vehicle due to their potential
for transdermal drug delivery.
Keywords: Microemulsions, Surfactant, Thermodynamically stable, amphiphile.
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