Modification of theophylline release with alginate gel formed in hard capsules |
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Authors: | Pornsak Sriamornsak Srisagul Sungthongjeeh |
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Institution: | (1) Department of Pharmaceutical Technology, Faculty of Pharmacy, Silpakorn University, 73000 Nakhon Pathom, Thailand;(2) Pharmaceutical Biopolymer Group, Faculty of Pharmacy, Silpakorn University, 73000 Nakhon Pathom, Thailand;(3) Department of Pharmaceutical Technology, Faculty of Pharmaceutical Sciences, Naresuan University, 65000 Phitsanulok, Thailand |
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Abstract: | The aim of this work was to establish whether alginate gel formed spontaneously in hard gelatin capsules which modifies release
of a model drug, theophylline. The effects of the alginate composition, the calcium addition, and the dissolution medium on
drug release were also investigated. After the capsule shell dissolved in water, at neutral pH the gel layer of sodium alginate
was formed immediately as the sodium alginate hydrated and swelled on contact with the aqueous medium. In acidic pH, the contents
remained intact and the matrix shape was the same. Theophylline release from capsules containing different grades of alginate
demonstrated different release patterns, depending on alginate composition and the pH of the medium. The capsules containing
sodium/calcium salts of alginate showed the slowest drug release at neutral pH but the fastest in acidic medium. The presence
of calcium acetate in the formulations influenced the drug release kinetics. The drug release in acidic medium showed a non-Fickian
diffusion-controlled release, while those in water at neutral pH exhibited a Super Case II transport mechanism. The study
also provides evidence that the behavior of alginate in forming the hydrated gel layer may explain the drug release behavior
at different pHs.
Published: July 6, 2007 |
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Keywords: | Alginate hydrogel matrices hard capsules controlled release sustained release theophylline |
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