Dispersions, controlled release polymers

S. Kockisch, G.D. Rees, S.A. Young, J. Tsibouklis, and J.D. Smart, A direct-staining method to evaluate the mucoadhesion of polymers from aqueous dispersion,/. Controlled Release, 77, 1-6, 2001. 

Matrix diffusion-controlled system in which the drug is homogeneously dispersed in a hydrophilic polymer diffusion from the matrix controls release rate Nitrodur (nitroglycerin key). 

These additives can also be placed into microcapsules with a thin polymer skin. For example, they are filled with natural aromas and applied to the textile from a water dispersion in combination with a polyurethane or silicone binder. The ratio of micro bubbles to binder determines the efficiency and permanence of the finish. Good results after 4-12 washing cycles are reported. The encapsulated materials are released during wearing as the micro bubbles burst from rubbing caused by body movement or by diffusion through the thin layer of the capsules. A market available encapsulation in micro bubbles, built from chitosan, is described by Hampe. The incorporation and controlled release of fragrance compounds is also provided by the sol-gel nano-technique described in Section 18.4. 

This controlled-release subdermal implant is fabricated by dispersing micronized estradiol crystals in a viscous mixture of silicone elastomer and catalyst and then coating the estradiol-polymer dispersion around a rigid (drug-free) silicone rod by an extrusion technique to form a cylinder-shaped implant (Fig. 11). This implant is designed for subcutaneous implantation in the steer s ear flap for a duration of 200 or 400 days, during which a controlled quantity of estradiol is released daily for growth promotion. 

Fig. 13 The controlled release of drug molecules from a (membrane-matrix) hybrid-type drug delivery system in which solid drug is homogeneously dispersed in a polymer matrix, which is then encapsulated inside a polymeric membrane, where D, P, and h are the diffusivity, permeability, and thickness, respectively, and the subscripts p, m, and d denote the drug depletion zone in the polymer matrix, polymer coating membrane, and diffusion layer, respectively.

Goracinova K, Klisarova L, Simov A, et al. Preparation, physical characterization, mechanisms of drug/polymer interactions, and stability studies of controlled-release solid dispersion granules containing weak base as active substance. Drug Dev Ind Pharm 1996 22(3) 255-262. 

Klinger GH, Ghalli ES, Porter SC, Schwartz JB. Formulation of controlled release matrices by granulation with a polymer dispersion. Drug Dev Ind Pharm 1990 16(9) 1473-1490. 

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