Drug solubilization advantages

Improvements in theophylline preparations have come from alterations in the physical state of the drugs rather than from new chemical formulations. For example, the increased surface area of anhydrous theophylline in a microcrystalline form facilitates solubilization for complete and rapid absorption after oral administration. Numerous sustained-release preparations (see Preparations Available) are available and can produce therapeutic blood levels for 12 hours or more. These preparations offer the advantages of less frequent drug administration, less fluctuation of theophylline blood levels, and, in many cases, more effective treatment of nocturnal bronchospasm. 

Examples of studies supporting use of emulsions for a variety of drug delivery needs are listed in Table 10.4. Some of the advantages conferred by emulsion formulations may be mediated by an improved solubilization of the drug. There is also a growing list of studies suggesting use of emulsions fordrug solubilization perse these are summarized in Table 10.5. 

Microemulsions Microemulsions (MEs) are colloidal dispersions composed of an oil phase, an aqueous phase, and one or more surfactants. They are optically isotropic and thermodynamically stable and appear as transparent liquids as the droplet size of the dispersed phase is less than 150 nm. One of their main advantages is their ability to increase the solubilization of lipophilic and hydrophilic drugs accompanied by a decrease in systemic absorption [217]. Moreover, MEs are transparent systems thus enable monitoring of phase separation and/or precipitation. In addition, MEs possess low surface tension and therefore exhibit good wetting and spreading properties. 

Each method listed in Table 1 has advantages and limitations, and there has been no universal formulation approach that can be applicable to various types of hydrophobic drugs. A solubilization method appropriate for a given drug has to be chosen depending on the physicochemical properties of the drug and the requirements for the final formulation such as the desired concentration, dose, stability, etc. 

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