The addition of cosolvents such as short chain alcohols imparts flexibility to the interface that is helpful for the free movement of the hydrophobic tails of surfactant at interface which in turn imparts dynamic behavior to microemulsions [ 32 ]. Dahan A, Hoffman A. The authors declare that there is no conflict of interests regarding the publication of this paper. Although many formulation approaches like solid dispersions, complexation, pH modification, and cocrystals exist, lipid based delivery systems finding increased appliance with the apparent increase in absorption of drug. Stimulation of body secretions that help in digestion of lipids:
Digestive lipids such as triglycerides, diglycerides, fatty acids, phospholipids, cholesterol [ 1 ], and other lipids based on synthetic origin offer improvement in bioavailability of the drug in contrast to the nondigestible lipids with which reduced bioavailability may occur due to impairment in absorption caused by retention of the fraction of administered drug in the formulation itself. Among various lipid based formulations liposomes, solid lipid nanoparticles, self-dispersing tablets, and solid solutions , self-microemulsifying formulations are receiving more attention by formulation scientists as these are advantageous in the aspect of their stability, self-dispersing nature, ease of preparation, and scale-up. Eur J Pharm Sci. The solubilization behavior of surfactant for the drug gained popularity due to its inhibitory effect on drug precipitation in vivo [ 30 ]. The opening of tight junctions by the surfactants also contributes to the improvement in permeability and this was explored with the study conducted by Sha et al. Coadministration of lipid with the lipophilic drug is as advantageous because it contributes to the enhancement of bioavailability of the drug by the following mechanisms. From this equation, it is evident that the lower the interfacial energy the lower the free energy.
Failure to attain intended therapeutic effect of the poor water soluble drugs by this route led to development of novel drug delivery systems which will fulfill therapeutic needs with minimum ssytem. Adv Drug Deliv Rev. Due to their high polarity, they tend to migrate towards aqueous phase upon dispersion into aqueous media leading to drug precipitation.
International Scholarly Research Notices. Faster and enhanced drug release can be attained with smaller droplets which in turn promotes bioavailability.
In view of the current investigation, due to a larger nanoemulsion region and a greater capacity for incorporation of oily phase, which is most desirable for OCH 3 -PPD, a Labrafil MCremphor EL-glycerin system was selected. Refractive index decreases with increase in cosurfactant concentration attributed to decrease in the rigidity of microemulsion structure and it increases with the increase in globule size [ 50 ].
The effect of dilution on microemulsion clarity can be evaluated by performing the dilution of microemulsion preconcentrate to various dilutions that simulate the gastric conditions and in various diluents like double distilled water, simulated gastric fluid SGFand simulated intestinal fluid SIF [ 37 ]. Triglycerides with long and medium chain length containing different degrees of saturation are commonly used in the preparation of SMEDDS [ 3 ].
The smaller the droplet size, the larger the interfacial surface area provided for drug absorption. Dahan A, Hoffman A. Usually the value of zeta potential is negative due to the presence of free fatty acids [ 30 ] but when cationic lipid such as oleylamine is used, the positive charge gets developed [ 3 ].
Then, aqueous phase penetrates through interface and gets solubilized within the oil phase up to the solubilization limit. Home Journals Why publish with us? The samples which formed clear solution should be denoted by suitable symbols in the phase diagram [ 47 ].
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Lipid Oils Oils are the important component of SMEDDS, as solubilization and access of the drug to the lymphatic circulation of poor water soluble drugs depend on the type and concentration of oil used for formulation.
The emulsification ability of surfactants can be known by mixing the equal proportions of selected oil and surfactant which is followed by homogenization. Isolation, structural determination, and evaluation of the biological activity of 20 S methoxyl-dammarane-3, 12, triol [20 S OCH 3 -PPD], a novel natural product from Panax notoginseng.
Ternary diagrams of the surfactant, cosurfactant, and oil were plotted, each representing an apex of the triangle.
Value of zeta potential indicates the stability of emulsion after appropriate dilution. In case of addition of fourth component, the ternary diagram can be called pseudoternary phase diagram as one of the corners corresponds to the mixture of two components like surfactant and cosurfactant [ 43 ].
[Full text] Self-microemulsifying drug-delivery system for improved oral bioavaila | IJN
This enhanced lymph delivery of the drug can bypass the first pass extraction whereby the bioavailability of drugs that undergo extensive first pass effect can be improved. If oil and aqueous phase have high diffusion coefficients and are of the same magnitude as pure components, it indicates the presence of bicontinuous type microemulsion [ 55 ].
Although natural surfactants are less toxic, the efficiency of self-emulsification is limited [ 3 ]. Eighty-four such mixtures with varying surfactant, cosurfactant, and oil concentrations were prepared for this investigation. mictoemulsifying
The free energy of conventional emulsion is very high as high energy is required to form new surface between two immiscible phases like oil and water. The rheology of microemulsion can be determined delicery the graph plotted between thesix stress and shear rate. Semisynthetic medium chain derivatives are superior to MCTs for the reason that they are amphiphilic in nature with surfactant properties [ 322 ].
Droplet size distribution is a critical factor when evaluating a self-microemulsion system. Selection of the surfactant was governed by emulsification efficiency Table 3.
The preparation involves the addition of drug to the mixture of oil, surfactant, and cosurfactant and then it should be subjected to vortexing [ 49 ]. As expected, compositions with lower absorbance showed the lowest droplet size because aqueous dispersions with small absorbance are optically clear and oil droplets are thought to be in a state of finer dispersion.