Sustained release systems

M., Pyrimethamine sustained release systems based on bioresorbable polyesters for chemoprophylaxis of rodent malaria,... 

Another approach to the pulsatile delivery of drugs with an osmotic pressure driven system has been suggested by Amidon et al. [66], This system provides the option of an immediate bolus dose and a second dose that can be timed to be released at some subsequent point following the administration of the dosage form. One or both of the doses can be composed of multiparticulates, for example, that would themselves be sustained release systems. 

Allen TM, Mehra T, Hansen C, et al. Stealth liposomes an improved sustained release system for 1-P-D-arabinofuranosylcytosine. Cancer Res 1992 52 2431. 

Methods were described for the incorporation of proteins in the form of noncovalent complexes with polycationic reagents, into sustained release systems where the polycation stabilizes the protein against inactivation while it resides in the delivery device, and retards release of the protein from the delivery device [469,470]. A variety of polycations have been used, including simple polyamino acids such as polylysine or polyarginine, protamine and chitosan. The end result was the release of the active agent with retention of biological activity, with a high cumulative field and over a sustained period of time. 

The dissolution controlled release matrix systems provide sustained release profiles i.e., the active drugs in these systems are released continuously at a slow rate to provide a long-term therapeutic effect. Unlike diffusion controlled release coated systems, release profiles from dissolution controlled release coated systems do not follow zero-order kinetics but fall within the classification of delayed release systems,4 pulsatile or repeat-action systems,5 and sustained release systems.3... 

One final point concerns the prevention of the inevitable release of active molecules into the external phase during storage in sustained release systems, referred to earlier. One potential way around this is to use a double-shell system. Here the inner shell imparts the sustained release properties, but the outer shell is impenetrable to the active molecules. Triggered breaking of this outer shell, at the required point in a given process, would then initiate the sustained release process. This topic is the focus of our current research in this subject. 

Microencapsulation has been the subject of massive research efforts since its inception around 1950. Today, it is the mechanism utilized by approximately 65% of all sustained-release systems [35], The technique s popularity can be attributed mainly to its wide variety of applications. Hundreds of drugs have been microencapsulated and used as controlled-release systems. Some examples are Arthritis Bayer, Dexatrim Capsules, and Dimetapp Elixir. 

Alza s GITS sustained-release system (September 2003) and... 

Formulation is a common method of developing sustained release preparations such as erosion tablets, drugs in a waxy matrix (matrix erodes or drug leaches from matrix), coated pellets (different pellets have different release properties), and coated ion-exchange preparations. There are special considerations for sustained release systems, since complicated formulations may be more erratically absorbed the sustained release product may contain a larger dose (and failure of the controlled release mechanism may result in release of a large toxic dose) and is a more expensive technology. 

Melia, C.D. (1991) HydrophUic matrix sustained release systems based on polysaccharide carriers. Crit Rev Ther Drug Carrier Syst, 8, 395 21. 

In Vivo Studies on Drug—Polymer Sustained-Release Systems... 

Anderson, J. M., Niven, H., Pelagalll, J., Olanoff, L. S., and Jones, R. D. "The Role of the Fibrous Capsule In the Function of -Implanted Drug-Polymer Sustained Release Systems"... 

Higashi, T., Hirayama, R, Arima, H., Uekama, K. Polypseudorotaxanes of pegylated insulin with cyclodextrins application to sustained release system. Bioorg. Med. Chem. Lett. 2007,17, 1871-1874. 

Purified fractions of the cartilage material were highly soluble, so that they disappeared quickly after they were added. Therefore, a small sustained-release system was needed to provide steady diffusion into the tumor. Such a system had to be inert and noninflammatory. In early work (3), polyacrylamide pellets had been tried for this purpose. The test... 

Murray, J., et al., A micro sustained release system for epidermal growth factor. In Vitro, 1983, 19, 743-748. 

Sidman, K.R., et al. Biodegradable, implantable sustained release systems based on glutamic acid copolymers, Journal of Membrane Science, 1980, 7, 277-291. 

Van Slooten M L, et al. (2001). Liposomes as sustained release system for human interferon-gamma Biopharmaceutical aspects. Biochim. Biophys. Acta. 1530(2-3) 134-145. 

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