Lipophilic drugs emulsions

Van Bloois, L., Dekker, D. D., and Crommelin, D. J. A. (1987). Solubilization of lipophilic drugs by amphiphiles Improvement of the apparent solubility of almitrine bismesylate by liposomes, mixed micelles and O/W emulsions, Acta Pharmaceut. TechnoL,... 

Topical Formulations. Topical formulations by their very nature are usually multicomponent, and it is not surprising that neural networks have been applied to deal with this complexity. The first work was performed on hydrogel formulations containing anti-inflammatory drugs in Japan in 1997 [57], followed up by further studies in 1999 [58] and in 2001 [59]. Lipophilic semisolid emulsion systems have been studied in Slovenia [60, 61] and transdermal delivery formulations of melatonin in Florida [62]. In all cases, the superiority of neural networks over conventional statistics has been reported. 

An excellent carrier is needed to deliver a sufficient amount of prostaglandins to the diseased site. Liposomes have been studied for a long time as possible drug carriers. However, the clinical use of liposomes has delayed because of some difficulties in mass production, sterilization, stability and safety. Since 1980 we have attempted to use lipid microspheres (lipid emulsions) instead of liposomes as a better carrier for lipophilic drugs (7). 

The self-emulsifying behaviour of a binary nonlonlc surfactant vegetable oil mixture has been shown to be dependant on both temperature and surfactant concentration. The quality of the resulting emulsions as assessed by particle size analysis showed that manipulation of these parameters can result In emulsion formulations of controlled droplet size and hence surface area. Such considerations are Important when the partition of lipophilic drugs Into aqueous phases and drug release rates are considered. 

Water Water is the primary raw material in pharmaceutical formulations. It is the most used vehicle since it is the major component of the human body. For many products, it is the main component, and, even in those containing non-water-soluble substances, water must be present. Depending on the product and the form of administration, lipophilic drugs are prepared as water-oil emulsions. 

Takino, T., Konishi, K., Takadura, Y., and Hashida, M. (1994) Long circulating emulsion carrier systems for highly lipophilic drugs.Biol. Pharm. Bull., 17 121-125. 

The presence of lipids in the GI tract stimulates gall bladder contracts and biliary and pancreatic secretions, including bile salts, phospholipids, and cholesterol. These products, along with the gastric shear movement, form a crude emulsion, which promotes the solubilization of the coadministered lipophilic drug. Exogenous surface-active agents incorporated into the formulation may further stimulate the solubilization of the lipophilic compound. 

In this technique, a hydrophobic polymer is dissolved in an organic solvent, such as chloroform, ethyl acetate, or methylene chloride and is emulsified in an aqueous phase containing a stabilizer (e.g., PVA). Just after formation of the nanoemulsion, the solvent diffuses to the external phase until saturation. The solvent molecules that reach the water-air interphase evaporate, which leads to continuous diffusion of the solvent molecules from the inner droplets of the emulsion to the external phase simultaneously, the precipitation of the polymer leads to the formation of nanospheres. The extraction of solvent from the nanodroplets to the external aqueous medium can be induced by adding an alcohol (e.g. isopropanol), thereby increasing the solubility of the organic solvent in the external phase. A purification step is required to assure the elimination of the surfactant in the preparation. This technique is most suitable for the encapsulation of lipophilic drugs, which can be dissolved in the polymer solution. 

Over the last decade, o/w nanosized emulsions containing either anionic or cationic droplets have been recognized as interesting and promising ocular topical delivery vehicles for lipophilic drugs. Complete details are available elsewhere [117]. As an overview of this topic, important results on emulsion-based ocular topical drug delivery are covered below and are listed in Table 5. 

Iwamoto, K., Kato, T., Kawahara, M., Koyama, N., Watanabe, S., Miyake, Y., and Sunamoto, J. (1991), Polysaccharide-coated oil droplets in oil-in-water emulsions as targetable carriers for lipophilic drugs, J. Pharm. Sci., 80, 219-224. 

Tamilvanan, S., and Benita, S. (2004),The potential of lipid emulsion for ocular delivery of lipophilic drugs, Eur. J. Pharm. Biopharm., 58, 357-368. 

Sterile parenteral oil-in-water emulsions have been used extensively for over 40 years for the intravenous administration of fats, carbohydrates, and vitamins to debilitated patients. Several vegetable oil-in-water emulsions are now available commercially with droplet sizes similar to that of chylomicrons (approximately 0.5-2 pm), the natural fat droplets in the blood that transport ingested fats to the lymphatic and circulatory systems (Table 1). More recently, such emulsions have been employed as intravenous carriers for poorly water-soluble lipophilic drugs such as vitamin K (e.g.. Sterile Phytonadione Injection U.S.P.) diazepam... 

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