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Development of hot-melt extrusion as a novel technique for the ...

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Fig. 8.4: HCS rele<strong>as</strong>e pr<strong>of</strong>iles in both coated and uncoated tablets. Each result shows <strong>the</strong>mean±S.D. (n = 3).The rele<strong>as</strong>e mechanism from <strong>the</strong> tablets can be described <strong>as</strong> a diffusion process <strong>of</strong> <strong>the</strong>drug through <strong>the</strong> slow rele<strong>as</strong>e polymers matrix. The slow dissolving nature <strong>of</strong> EC polymershinders <strong>the</strong> dissolution medium penetration and consequently controls <strong>the</strong> drug dissolutionand diffusion rate [25] . While processing through HME <strong>the</strong> active substance w<strong>as</strong> covered byEC matrix which resulted in retarded rele<strong>as</strong>e <strong>of</strong> HCS over 12 hrs. Moreover, <strong>the</strong> polymericcoating level indicated a controlling effect due to its slow dissolution, irrespective <strong>of</strong> <strong>the</strong>tablet composition. Lower coating levels (15%) allowed greater penetration <strong>of</strong> <strong>the</strong> dissolutionmedium.3.7 Analysis <strong>of</strong> rele<strong>as</strong>e mechanismAnalysis w<strong>as</strong> per<strong>for</strong>med by <strong>the</strong> above equations using water <strong>as</strong> <strong>the</strong> dissolution testmedium. Obtained results <strong>for</strong> rele<strong>as</strong>e rate constants <strong>as</strong> well <strong>as</strong> R 2 values <strong>for</strong> all tablets aresummerized in table 8.3. Nei<strong>the</strong>r coated nor uncoated tablets fit with equation (8.1), zeroorder rele<strong>as</strong>e model, which represents zero order kinetics. Concerning equations (8.2)–(8.6),regression analyses were per<strong>for</strong>med in <strong>the</strong> ranges in which linearity w<strong>as</strong> observed. The firstorder kinetics model plot shows <strong>the</strong> relationship between <strong>the</strong> logarithm <strong>of</strong> <strong>the</strong> drug residual162 | P a g e

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