Drug delivery systems microspheres

An example of such a product is Sterile Medroxyprogestrone Acetate Suspension used for its contraceptive property. Such an injection is designed to provide up to three months of contraceptive activity. Another such product is a depot injection of leuprolode acetate, an analogue of gonadatropin-releasing hormone (see Drug delivery systems). In this case, the product is a sterilized powder of microspheres to be suspended upon the addition of an appropriate diluent and intended for monthly injection. 

A large variety of drug delivery systems are described in the literature, such as liposomes (Torchilin, 2006), micro and nanoparticles (Kumar, 2000), polymeric micelles (Torchilin, 2006), nanocrystals (Muller et al., 2011), among others. Microparticles are usually classified as microcapsules or microspheres (Figure 8). Microspheres are matrix spherical microparticles where the drug may be located on the surface or dissolved into the matrix. Microcapsules are characterized as spherical particles more than Ipm containing a core substance (aqueous or lipid), normally lipid, and are used to deliver poor soluble molecules... 

As discussed earlier, noncollagenous proteins, particularly albumin and to a lesser extent gelatin, in the form of microspheres and nanoparticles continue to be exploited as drug delivery systems. Oppen-heim (71) and Speiser (72) reviewed the technology developed to produce ultrafine particles, often referred to as nanoparticles. 

Lipid Microspheres and Lecithinized-Polymer Drug Delivery Systems... 

Recently, biodegradable polymers have been used to fabricate macro- and nanometer scale self-assembled systems such as microspheres (MSs), nanospheres (NSs), polymer micelles, nanogels, and polymersomes (Fig. 1). These have attracted growing interest because of their potential utility for drug delivery systems (DDS), tissue engineering, and other applications. To construct these self-assembled systems... 

Ilium, L., Jorgensen, H., Bisgaard, H., Krogsgaard, O., and Rossing, N., Bioadhesive microspheres as a potential nasal drug delivery system, Int. J. Pharm., 39 189-199 (1987). 

The use of albumin microparticles as a drug delivery system was first suggested by Kramer (1974) and several methods for their production were subsequently developed (Gupta and Haung 1989). Most methods involved the application of emulsification methodology and factors involved in this process have been evaluated by a number of authors. However, studies of the in vitro disintegration process of protein microspheres, induced by the presence of protease enzymes in the environment, are limited (El-Samaligy and Rohdewald 1983). 

Lee, J.H., T.G. Park, and H.K. Choi. 1999. Development of oral drug delivery system using floating microspheres. J Microencapsul 16 715. 

Soppimath, K.S. 2001. Microspheres as floating drug-delivery systems to increase gastric retention of drugs. Drug Metab Rev 33 149. 

Wang, J., et al. 2000. Positively charged gelatin microspheres as gastric mucoadhesive drug delivery system for eradication of H. pylori. Drug Deliv 1 231. 

Different drug delivery systems have been proposed for vaginal delivery of peptides and proteins. The first one was a mucoadhesive gel based on polyacrylic acid intended for vaginal administration of insulin [96]. More recently, microparticulate systems such as starch and hyaluronan ester (HYAFF) microspheres have been proposed for vaginal delivery of insulin... 

Mathiowitz, E., Jacob, J. S., Jong, Y. S., et al. Biologically erodable microspheres as potential oral drug delivery systems. Nature 386 410—414, 1997. 

Based on these limitations, only a limited number of drug delivery systems based on biodegradable polymers have so far been successfully commercialized. One example is Lupron Depot one-month injectable microspheres of PLGA containing leuprorelin acetate (LH-RH agonist) for the treatment of endometriosis and prostatic cancer [31,32]. 

TABLE II. Requirements for microsphere drug delivery systems... 

Activation, dextran and inulin, 189-195 Activation energy of diffusion, 50-52 Additives, effect on percutaneous absorption of drugs in rabbits, 275 Agarose gel, use in liposomal drug delivery system, 267-270 Albumin microspheres intramuscular and intraarticular drug delivery, 204,206,211 preparation, 204,207/... 

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