Emulsions oral drug delivery systems

Various coUoidal systems formed with block or graft copolymers, such as liposomes, microspheres, emulsions have been described for oral drug-delivery systems. Block and graft copolymers in their micellar form or as steric stabilizers for colloidal particles are well suited for oral and injectable drug formulations and diagnostic systems if they meet the requirement of biocompatibility and preferably of biodegradability [278,279]. 

Ghosh LK, Ghosh NC, Thakur RS, Pal M, Gupta BK. 1997. Design and evaluation of controlled-release W/O/W multiple-emulsion oral liquid delivery system of chlorpheniramine maleate. Drug Dev Ind Pharm 23 1131-1134. 

The use of ttaditional disperse systems, e.g., macroemulsions, in the pharmaceutical industry has been limited due to manufacturing complexity and stability problems [117]. The characteristic properties of nano-emulsions (kinetic stability, small and controlled droplet size, etc.) make them interesting systems for pharmaceutical applications. Indeed, nano-emulsions are used as drug delivery systems for administration through various systemic routes. There are numerous publications on nano-emulsions as drug delivery systems for parenteral [17,18,28,29,118-124], oral [25,125-129], and topical administration, which includes the administration of formulations to the external surfaces of the body skin [32,130,131] and to the body cavities nasal [30,132] as weU as ocular administration [31,133-136]. Moreover, many patents concerning pharmaceutical applications of nano-emulsions have been registered [17,18,25,137-145]. An application of nano-emulsions in this field has been in the development of vaccines [33,146-147]. 

In many cases in drug development, the solubility of some leads is extremely low. Fast dissolution rate of many drug delivery systems, for example, particle size reduction, may not be translated into good Gl absorption. The oral absorption of these molecules is usually limited by solubility (VWIImann et al., 2004). In the case of solubility limited absorption, creating supersaturation in the Gl Luids for this type of insoluble drugs is very critical as supersaturation may provide great improvement of oral absorption (Tanno et al., 2004 Shanker, 2005). The techniques to create the so-called supersaturation in the Gl Luids may include microemulsions, emulsions, liposomes, complexations, polymeric micelles, and conventional micelles, which can be found in some chapters in the book. 

In pharmaceutical preparations, soybean oil emulsions are primarily used as a fat source in total parenteral nutrition (TPN) regimens. Although other oils, such as peanut oil, have been used for this purpose, soybean oil is now preferred because it is associated with fewer adverse reactions. Emulsions containing soybean oil have also been used as vehicles for the oral and intravenous administration of drugs drug substances that have been incorporated into such emulsions include amphotericin, " diazepam, retinoids, vitamins, poorly water-soluble steroids, fluorocarbons, and insulin. In addition, soybean oil has been used in the formulation of many drug delivery systems such as liposomes, microspheres, dry emulsions, self-emulsifying systems, and nanoemulsions and nanocapsules. ... 

SLM combines the advantages of different drug delivery systems such as polymeric microparticles, fat emulsions, and liposome. In this respect, they have been successfully proposed for the delivery of a variety of drugs including antibiotics, anti-inflammatory compounds, vaccines, and adjuvant. Among the hpids, phospholipids, triacyl glycerols, waxes, fatty acids, or their mixtures can be used. SLM can be administered by subcutaneous, oral, intramuscular, topical, or pulmonary ways. 

Recently, a new oral sustained drug delivery system has been proposed. Ii is referred to as dry adsorbed emulsion (2,3). To form a dry adsorbed emulsion, a water-in-oil (W/0) emulsion was prepared. The aqueous phase of the W/O emulsion contained a hydrophilic active drug. After the emulsion preparation, both phases of the W/O emulsion were stabilized by two inactive powders. In previous works, the first powder was a highly polar silica and could absorb the aqueous phase. The second powder was a hydrocarbon-bonded silica with a low polarity compatible with the oil phase of the W/O emulsion. The finished form was a fluid powder whose particle size diameter ranged from 300 to 2000 pm. Sodium salicylate was used as a model of hydrophilic active drug (2-6). The experiment showed the following ... 

The dry adsorbed emulsions are easy to prepare industrially (without any u.se of solvents) and their different particle sizes convenient to handle. Particles of dry adsorbed emulsions are incorporated in hard gelatin capsules or tablets to obtain a sustained drug delivery system for oral route that is well accepted by patients. The sustained relea.se effect depends mainly on the particle size of (he form, on the composition of the primary emulsion oil phase, and on the process of manufacturing, The adsorbent and drug nature and physicochemical properties are al.so important in the drug release profile. 

A Berthod, M Rollet, N Farah. Dry adsorbed emulsions an oral sustained drug delivery system. J Phami Sci 77 2)6-221, 1988,... 

Berthod, A., RoUet, M., and Farah, N. 1988. Dry adsorbed emulsions An oral sustained drug delivery system. J. Pharmacol. Sci. 77 216-221. 

In the following, lipid-based systems for oral drug delivery of peptides and proteins have been classified into liposomes and emulsions, although the distinction between these classifications is somewhat vague. 

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