Swelling-controlled release

In swelling-controlled systems, glassy hydrogels ia particular, the release process is a combination of the diffusion of water iato the system and dmg from the system. Empirically, release from these systems may be expressed as (83) ... 

GWR Davidson IH, NA Peppas. Solute and penetrant diffusion in swellable polymers. VI. The Deborah and swelling interface numbers as indicators of the order of biomolecule release. J Controlled Release 3 259-271, 1986. 

Fig. 2. Schematic representation of the behavior of a one-dimensional swelling controlled release system. The water (W) penetrates the glassy polymer (P) to form a gel. The drug (D) is released through the swollen layer.

Allow, when swelled, controlled release of the active compound ... 

Mandal, T.K. 2000. Swelling-controlled release system for the vaginal delivery of miconazole. Eur... 

Colombo, P., Santi, P., Bettin, R., Brazel, C., and Peppas, N. Drug release from swelling-controlled sytems, in Wise, D. (ed.), Handbook of Pharmaceutical Controlled Release Technology. New York Marcel Dekker, 2000, pp. 183-210. 

Podual K, Doyle F, and Peppas NA. Modeling of water transport in and release from glucose-sensitive swelling-controlled release systems based on poly(diethylaminoethyl methacrylate-g-ethylene glycol). Industrial engineering chemistry research 2004 43 7500-7512. 

Korsmeyer, R.W. Peppas, N.A. Macromolecular and modeling aspects of swelling-controlled systems. In Controlled Release Delivery Systems Roseman, T.J., Mansdorf, S.Z, Eds. Marcel Dekker, Inc. New York, 1983 77-90. 

Colombo P. Swelling-controlled release in hydrogel matrices for oral route. Adv Drag Deliv Rev 1993 11 37-57. 

Solvent-activated systems either by (a) Osmotically controlled systems or (b) Swelling-controlled systems, and (4) Modulated-release systems. Nevertheless it can be added the fifth category (5) Combined mechanisms because it could be observed drug delivery devices that act by a combination of above mentioned mechanisms. Bajpai schematically further explain cited basics mechanisms of control (Bajpai et al. 2008). 

The exact mechanism that governs the drug release is stiU dealt with some controversy. A swelling-controlled mechanism is often suggested based on a simple data fitting to a mathematical model (15,16). 

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