Water-based silicone elastomer controlled release tablet film coating
Abstract
Membrane controlled release systems have played a major role in oral controlled drug delivery. An emulsion which is a polymerized and cross-linked latex product of hydroxyendblocked polydimethylsiloxane and an alkoxysilane has been developed as a controlled release tablet film coating system. With adequate reinforcement of colloidal silica, the silicone elastomer latex yielded solid elastomeric free films upon drying. Polyethylene glycols of different molecular weights were incorporated in the coating system to enhance the permeability of the silicone elastomer to hydrophilic and ionic species. Free films derived from the three-component silicone elastomer dispersions were evaluated by various physical and chemical methods with respect to their suitability as an aqueous controlled release film coating system. The ability of the formulated silicone elastomer dispersions to produce stable controlled release tablet film coatings was further evaluated using potassium chloride as the model compound. The effects of coating composition, non-formulation factors and coating process variables on the controlled release behavior of the silicone elastomer coating system were determined. The molecular weight and loading level of polyethylene glycol used as well as the silicone to silica ratio in the coating were shown to dictate the release pattern of the active ingredients from the coated tablets. Coating process effects were also found to be significant. The capability of the formulated silicone elastomer coating to provide controlled release for therapeutic agents of different physicochemical properties and dose levels was also demonstrated. Both the rate and extent of release of the therapeutic agents could also be altered by the type of diluent used in the tablet matrix. The drug release from the coated tablet system was achieved by an osmotic pumping effect and the diffusion through water-filled pores generated by the leaching of polyethylene glycol. The relative contribution of these two mechanisms to the overall drug release was dependent on the properties of the active ingredient and the composition of the coating.
Degree
Ph.D.
Advisors
Peck, Purdue University.
Subject Area
Pharmacology
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