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Title: Drug release kinetics of bilayer-coated spheroids
Authors: Wan, L.S.C. 
Tan, Y.T.F.
Heng, P.W.S. 
Keywords: Controlled release
Hydroxypropylmethyl cellulose
Release kinetics
Sodium carboxymethyl cellulose
Swelling dynamics
Issue Date: Mar-1998
Citation: Wan, L.S.C.,Tan, Y.T.F.,Heng, P.W.S. (1998-03). Drug release kinetics of bilayer-coated spheroids. S.T.P. Pharma Sciences 8 (2) : 113-122. ScholarBank@NUS Repository.
Abstract: Bilayer coating of drug spheroids with a fixed inner coat of plasticized hydrophilic cellulose ether and varying amount of plasticized methacrylic acid copolymer outer coat was formulated. These coated spheroids were able to demonstrate a greater sustained-release effect at pH 1 than spheroids coated with solely plasticized methacrylic acid copolymer. The swelling dynamics of the cellulose ether had an important role in achieving the desirable sustained release property as was well demonstrated by spheroids coated with an inner coat of plasticized hydroxypropylmethyl cellulose of high viscosity grade and an outer coat of plasticized Eudragit L30D. However, substituting the inner coat with fast-disintegrating sodium carboxymethyl cellulose of moderate viscosity grade was less superior in its sustained release effect than an interior coat of plasticized hydroxypropylmethyl cellulose. When plasticized methacrylate ester copolymer was utilized as the outer coat, the incorporation of plasticized cellulose ether, whether hydroxypropylmethyl cellulose or sodium carboxymethyl cellulose, as the inner coat, showed faster release than the plasticized Eudragit RS30D coat alone at both pH I and pH 7.2. Nevertheless, the results provided a useful basis for the design and formulation of bilayer coated spheroids consisting of a swellable inner layer, made of high viscosity plasticized hydroxypropylmethyl cellulose and an outer coat of an enteric material. The undissolved and intact membrane coat that swelled to different extent was directly correlated to the coating level or thickness of the outer L30D-PEG6000 coat. The swollen coat had attained a constant diffusion pathway for drug release, exhibiting a zero- order drug release kinetics at gastric pH.
Source Title: S.T.P. Pharma Sciences
ISSN: 11571489
Appears in Collections:Staff Publications

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