Dispersions drug delivery

Michael J. Groves, a pharmacist with a doctorate in chemical engineering, has spent much of his career working in industry and academe. Now retired, his scientific interests include dispersed drug delivery systems and quality control issues for parenteral drug products. Editor or joint editor of a number of books, he has published 400 research papers, patents, reviews, and book reviews. He is a Fellow of the Royal Pharmaceutical Society of Great Britain, the Institute of Biology, and the American Association of Pharmaceutical Scientists. 

Cyclodexttins, as cyclic oligosaccharides consisting of glucopyranose, with a UpophUic central cavity and a hydrophilic outer surface, have had a relevant role in the design of dispersed drug delivery systems such as microcapsules (Loftsson and Duchene, 2007). Cyclodextiins ability to increase availability of hydrophobic drag fiom dispersed systems still positions them as attractive excipients. 

Brouwer T, Todd DB et al (2002) Flow characteristics of screws and special mixing enhancers in a co-rotating twin screw extruder. Int Polym Process 17(l) 26-32 Carpenter J, Katayama D et al (2009) Measurement of Tg in lyophilized protein and protein exdpient mixtures by dynamic mechanical analysis. J Therm Anal Calorim 95 881-884 Chiang P-C, Ran Y et al (2012) Evaluation of drug load and polymer by using a 96-well plate vacuum dry system for amorphous solid dispersion drug delivery. AAPS Pharm Sci Tech 13(2) 713-722 Chokshi RJ, Sandhu HK et al (2005) Characterization of physico-mechanical properties of in-domethadn and polymers to assess their suitability for hot-melt extrusion process as a means to manufacture sohd dispersion/solution. J Pharm Sci 94(11) 2463-2474... 

The investigation of semi-solid objects such as lipid membranes [34], liquid crystalline dispersions [35, 36], drug delivery systems [37], food [38] and also... 

R Bodmeier, O Paeratakul. Suspensions and dispersible dosage forms of multiparticulates. In I Ghebre-Sell-assie, ed. Multiparticulate Oral Drug Delivery. New York Marcel Dekker, 1994, pp 143-157. 

Drug delivery to the respiratory tract has been characterized in the past decade by an increase in knowledge of drug droplet or particle manufacture, behavior, aerosol dispersion, lung deposition and clearance. The number of diseases for which aerosol therapy may be applicable has increased dramatically. The pharmaceutical scientist is no longer limited to pulmonary diseases as therapeutic targets. Substantial progress has been made in every area of pharmaceutical aerosol science, and it is anticipated that this will ultimately lead to many new therapies. 

Rekhi, G. S., Mendes, R. W., Porter, S. C., and Jambhekar, S. S., Aqueous Polymeric Dispersions for Controlled Drug Delivery - Wurster Process, Pharm. Technol., 13(3) 112-125 (1989)... 

Other surface-active compounds self-assemble into bilayer structures (schematically illustrated in Fig. 10b), which normally spherilize into structures termed vesicles. When vesicles are formed from phospholipids, the term liposome is used to identify the structures, which also provide useful drug delivery systems [71]. Solutes may be dispersed into the lipid bilayer or into the aqueous interior, to be subsequently delivered through a variety of mechanisms. Liposomes have shown particular promise in their ability to act as modifiers for sustained or controlled release. 

Solid dispersions have been explored as drug delivery systems for over 30 years, initially starting with various forms of polyethylene glycols, citric and succinic acids, and sugars. However, more recent success has been achieved using hydroxypropy-lcellulose (HPC), ethylcellulose (EC), and the commercial forms of methylacrylic acids and their copolymers sold under the name Eudragits. In addition, chitosans have been evaluated for this purpose. 

Most coacervates explored as drug delivery systems consist of particles dispersed in a liquid continuum. The questions as to how these systems are made and how they may be presented as drug delivery systems depends to a large degree on the individual formulator. 

As noted, phospholipids as a class tend to be only partially soluble in oil or in water. In the presence of water, for example, dispersed phospholipids tend to form characteristic structures under predetermined conditions. Examples of these would be the linear pairing, inside and out, of cellular bilayers and, as an extension, the unique hollow spherical structures of free phospholipids called liposomes which have proved to be valuable as drug delivery systems. 

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