Drug delivery control mechanisms

JUERGEN SIEPMANN is Professor of Pharmaceutical Technology, Universite Lille Nord de France, Lille, France. He received his Ph.D. from the Freie Universitaet Berlin, Berlin, Germany, in 1999. Since 2006, Dr. Siepmann has been Head of Controlled Drug Delivery Systems Mechanisms and Optimization, a research group. He is also Reviews Editor of the International journal of Pharmaceutics and is on the editorial boards of the journal of Controlled Release, the European journal of Pharmaceutics and Biopharmaceutics, the European journal of Pharmaceutical Sciences, and Drug Development and Industrial Pharmacy, among others. 

Since the development of the Spansule brand (Smith Kline Beech am) of coated beads and granules in the late 1960s, various dmg product technologies have been developed and patented to achieve extended durations of therapeutic effects. Each of these does so by various mechanisms of control of dmg release from adrninistered dosage forms. Each method has its advantages and disadvantages, a discussion of which is available in the pharmaceutical hterature (see Drug delivery systems) (21). 

Historically, the oral route of administration has been used the most for both conventional and novel drug-delivery systems. There are many obvious reasons for this, not the least of which would include acceptance by the patient and ease of administration. The types of sustained- and controlled-release systems employed for oral administration include virtually every currently known theoretical mechanism for such application. This is because there is more flexibility in dosage design, since constraints, such as sterility and potential damage at the site of administration, axe minimized. Because of this, it is convenient to discuss the different types of dosage forms by using those developed for oral administration as initial examples. 

P Colombo, R Bettini, P Santi, A De Ascentiis, NA Peppas. Analysis of the swelling and release mechanisms from drug delivery systems with emphasis on drug solubility and water transport. J Controlled Release 39 231-237, 1996. 

Park, J.-H., Allen, M.G. and Prausnitz, M.R. (2005) Biodegradable polymer microneedles fabrication, mechanics and transdermal drug delivery. Journal of Controlled Release, 104, 51-66. 

Bioerodible polymers offer a unique combination of properties that can be tailored to suit nearly any controlled drug delivery application. By far the most common bioerodible polymers employed for biomedical applications are polyesters and polyethers (e.g., polyethylene glycol), polylactide, polyglycolide and their copolymers). These polymers are biocompatible, have good mechanical properties, and have been used in... 

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. 

Silicones are frequently used in transdermal drug delivery. Recently, the use of loosely cross-linked silicone elastomer blends for this application was surveyed.537 The mechanisms of controlled drug release in the silicone-based systems have been studied,538 as silicones are evaluated for relatively new protein drug-delivery systems.5... 

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