Investigations on the Physical Structure and the Mechanism of Drug Release from an Enteric Matrix Microspheres with a Near-Zero-Order Release Kinetics Using SEM and Quantitative FTIR |
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Authors: | Wasfy M Obeidat Safwan M Obeidat Nizar M Alzoubi |
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Institution: | (1) College of Pharmacy, University of Sharjah, P.O. Box 27272, Sharjah, UAE;(2) College of Science, Philadelphia University, P.O. Box 1, Amman, 11392, Jordan;(3) College of Pharmacy, Applied Science University, P.O. Box 926296, Amman, 11931, Jordan;(4) Jordan University of Science and Technology, P.O. Box 3030, Irbid, 22110, Jordan |
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Abstract: | The objectives of this study were to evaluate the physical structure and the release mechanisms of theophylline microspheres
made of Eudragit S 100 polymer as an enteric polymer, combined with a nonerodible polymer, Eudragit RL 100. In the preparation
process, polymer combinations (1:1) were dissolved in an organic solvent mixture composed of acetone and methanol at a specific
ratio containing a theoretical drug loading of approximately 15%. Two microsphere formulations (LS1 and LS2) were prepared
at two different total polymer concentrations (10% in LS1 and 12.7% in LS2). Dissolution studies were carried out using US
Pharmacopeia Dissolution Apparatus II in an acidic medium for 8 h and in an acidic medium (2 h) followed by a slightly basic-buffered
medium for 10 h. Both LS1 and LS2 microsphere formulations produced particles that were spherical in shape and had very narrow
size distributions with one size fraction comprising 70–80% of the yield. Scanning electron microscopy and quantitative Fourier
transform infrared were used for microsphere physical structure evaluation. Except for the absence of drug crystals, photomicrographs
of both LS microspheres after dissolution in pH 1.2 and 7.2 buffer solutions were similar to those before dissolution. Dissolution
results indicated the ability of LS microspheres to minimize drug release during the acid stage. However, in the slightly
basic medium that followed the acidic stage, the drug release was sustained and controlled in its kinetics and data fitted
to Peppas equation indicated a case II transport suggesting that the drug release is mainly through swelling/erosion mechanism. |
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Keywords: | enteric FTIR microspheres narrow size SEM |
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