Abstract
Poorly water-soluble drug candidates are becoming more prevalent. It has been estimated that approximately 60–70% of the drug molecules are insufficiently soluble in aqueous media and/or have very low permeability to allow for their adequate and reproducible absorption from the gastrointestinal tract (GIT) following oral administration. Formulation scientists have to adopt various strategies to enhance their absorption. Lipidic formulations are found to be a promising approach to combat the challenges. In this review article, potential advantages and drawbacks of various conventional techniques and the newer approaches specifically the self-emulsifying systems are discussed. Various components of the self-emulsifying systems and their selection criteria are critically reviewed. The attempts of various scientists to transform the liquid self-emulsifying drug delivery systems (SEDDS) to solid-SEDDS by adsorption, spray drying, lyophilization, melt granulation, extrusion, and so forth to formulate various dosage forms like self emulsifying capsules, tablets, controlled release pellets, beads, microspheres, nanoparticles, suppositories, implants, and so forth have also been included. Formulation of SEDDS is a potential strategy to deliver new drug molecules with enhanced bioavailability mostly exhibiting poor aqueous solubility. The self-emulsifying system offers various advantages over other drug delivery systems having potential to solve various problems associated with drugs of all the classes of biopharmaceutical classification system (BCS).
Highlights
Various strategies have been widely investigated to enhance the bioavailability of poorly absorbed drugs in order to increase their clinical efficacy when administered orally
These generally consist of a drug dissolved in a blend of excipients (5 classes of excipients) with wide variety of physicochemical properties ranging from pure triglyceride oils, mono- and diglycerides, and substantial proportion of lipophilic or hydrophilic surfactants and cosolvents.Table 2 gives the broad classification system for various lipid formulations [19]
The results suggested that there might be a complex relationship between liquid crystal (LC) formation and emulsion formation
Summary
Various strategies have been widely investigated to enhance the bioavailability of poorly absorbed drugs in order to increase their clinical efficacy when administered orally. Various physicochemical properties which contribute to the poor solubility of various drugs include their complex structure, size, high molecular weight, high lipophilicity, compound H-bonding to solvent, intramolecular H-bonding, intermolecular Hbonding (crystal packing), crystallinity, polymorphic forms, ionic charge status, pH, and salt form [4]. Poorly soluble drugs can be formulated in three different forms to overcome the challenge of poor absorption—crystalline solid formulations, amorphous formulations, and lipid formulations [6]. Modification of the physicochemical properties such as salt formation and micronization of the crystalline compound to increase the surface area and dissolution may be one approach to improve the dissolution rate of the drug.
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