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Water-Insoluble Drug Delivery

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     Water-Insoluble Drug Delivery

 

A general description of water-insoluble drug delivery can be referred to the following table.

 Techniques  Descriptions
 Complexation A complex is a species of definite substrate-to-ligand stoichiometry that can be formed in an equilibrium process, in solution, and also in the solid state. Water-soluble ligands, such as cyclodextrins, can be used to solubilize water-insoluble substrate, such as ibuprofen.
 Cosolvents A water-miscible organic solvent that is used to increase the aqueous solubility of a water-insoluble drug by utilizing the lipophilicity of organic solvent which is more affinity to the lipophilic water-insoluble drug.
 Emulsions Colloidal dispersions of at least two immiscible phases, oil phase and aqueous phase, stabilized with the aid of a third component generally referred to as the emulsifying agent, or surfactant.  Water-insoluble drugs with the oil soluble property can be solubilized in the oil phase.
 Microemulsions Thermodynamically stable species, with much smaller droplet diameter (6 to 80 nm) and thus are visually transparent or translucent.  In addition to the aqueous phase, oily phase, and surfactant, they have a “cosurfactant,” and the proportions of the components are chosen such that they are in a stable region of the respective phase diagram; oil content is generally 2-20% percent.  Unlike conventional emulsions, microemulsions form spontaneously on mixing with little or no mechanical energy applied.
 Micelles A special form of self-aggregated complex in which the interactant is a surfactant, a molecule possessing both a nonpolar and a polar portion. A water-insoluble drug usually is affinity to nonpolar portion of the surfactant.
 Polymeric Micelles The substance forms a polymeric micelle is usually copolymers rather than conventional surfactant. Polymeric micelle formation occurs as a result of two forces. One is an attractive force that leads to the association of molecules while the other one a repulsive force, prevents unlimited growth of the micelles to a distinct macroscopic phase. Amphilphilic copolymers form micellar structures through self-association of the insoluble segments when placed in a solvent such as water.
 Liposomes Liposomes are vesicles formed by either synthetic or nature phospholipids.  These phospholipid molecules arrange themselves spontaneously into bilayer structures in water, so that the hydrophobic tails are shielded from water by hydrophilic heads.  Vesicles can consist of one or more phospholipid bilayers with hydrophilic and hydrophobic compartments.  The hydrophobic compartments can carry or fill with hydrophobic or water-insoluble drugs while the hydrophilic compartments can load hydrophilic or water-soluble drugs.
 Pharmaceutical Salts The salt is form by a water-insoluble drug, either a weak base or a weak acid, and a counterman, either a strong acid or a strong base.  The resultant salt, as an ionized form in water, is usually more soluble than the nonionized form.
 Prodrugs Prodrug is a drug with covalently bound, inactive moiety (the promoiety) which provides the desired pharmaceutical properties, where the promoiety must be removed upon administration to regenerate the parent drug in the body. The prodrug alternations possible following chemical modification of the parent drug include changes in the solubility properties.
 Particle Size Reduction Particle size reduction offers a significant opportunity for formulators to solve the product development hurdles inherent with water-insoluble drugs. The drug absorption enhancement of the insoluble drug is achieved by increasing the specific surface area in order to increase the dissolution.
 Solid dispersion A pharmaceutical solid dispersion is an intimate mixture of a drug substance (solute) with a diluent, termed a carrier (solvent or continuous phase).  Solid dispersion is used to enhance dissolution and improve the oral bioavailability of a water-insoluble drug via dispersing the finite drug particles in the carriers and enhancing its total surface area.
 Solid state alternation  An insoluble drug usually possesses one or more polymorphs, solvents and one amorphous forms.  By identifying and selecting one of these forms, which has highest solubility, the solubility of the water-insoluble drug can be enhanced.
 Softgel Technology Formulating the oily soluble drug in liquid formulation, which is filled in a soft gelatin capsule, can increase solubility of a water-insoluble drug, which is oil soluble.
 Percolation Percolation is a solubilizing system used in solid formulation to enhance drug dissolution by using a percolation matrix.  By carefully identifying critical concentrations of solubilizing agents, which are related to percolation thresholds in a percolation system, the dissolution of the insoluble drug can be enhanced.

 



     
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