Pharmaceutical Technology: Controlled Drug Release, Volume 2

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MULTIPARTICULATES [CH. 12 135 Fig. 3—Influence of thermal treatment on the drug release from tablets containing 15% HMW DL-PLA, 60% theophylline and 25% microcrystalline cellulose. The data in Figs 5 and 6 show dissolution profiles of theophylline from tablets containing low molecular weight DL-PLA. These profiles demonstrated that there was no significant difference in the dissolution release rate between the heated and non-heated tablets for both the 25% and the 60% theophylline formulations. In all cases, the tablets disintegrated within minutes and 100% of the theophylline was released within 1h. These results suggested that, regardless of the thermal treatment, low molecular DL-PLA had less of a binding capacity than the high molecular weight DL-PLA. Although thermal treatment increased the hardness of the tablet, it still rapidly disintegrated in water at 37°C. Dissolution studies were conducted at 37°C, which is above the glass transition temperature of the low molecular weight DL-PLA. The T g of this polymer is 27° C. Above the glass transition temperature, the chains of the polymer become more flexible and may loosen the binding capacity of the polymer in the tablet matrix, as evidenced by the rapid disintegration of the tablets when exposed to water at 37°C. The dissolution profiles in Figs 7 and 8 for theophylline tablets containing a low molecular weight L-PLA, microcrystalline cellulose, and theophylline. Thermal treatment had no significant effect on the dissolution profiles from tables containing 25% theophylline (Fig. 7). As with the tablets containing low molecular weight DL- PLA, these tablets disintegrated rapidly, releasing 100% theophylline within 1 h. However, the dissolution rate of theophylline from tablets containing 60% drug was accelerated from the thermally treated tablets when compared with the non-thermally treated tablets (Fig. 8). Although these tablets disintegrated within hours, the
136 CH. 12] BIODEGRADABLE POLYMERS Fig. 4—Influence of thermal treatment on the drug release from tablets containing 15% PCL-300 and 700, 25% theophylline and 60% microcrystalline cellulose. thermally treated tablets disintegrated faster then the non-thermally treated tablets. Low molecular weight L-PLA degrades rapidly at high temperatures, which may explain the rapid release of drug from the heat-treated tablets. This degradation of polymer, causing a decrease in moleular weight, may produce changes in the physicomechanical properties of the polymer, such as altering the degree of crystallinity and lowering the glass transition temperature. This is turn may promote faster disintegration of the tablet matrix when exposed to temperatures above the polymer glass transition temperature. CONCLUSIONS Thermally treated tablets containing high molecular weight DL-PLA and PCL-300 demonstrated a retardation in the dissolution release rate of theophylline from tablet compacts containing 60% microcrystalline cellulose, while thermally treated tablets containing low molecular DL-PLA showed no significant change in the drug dissolution rate when compared with non-thermally treated tablets. In contrast, tablets containing low molecular weight L-PLA showed an acceleration in the dissolution rate after thermal treatment. These results suggest that the physicochemical properties of the polymers, in combination with thermal treatment, have a significant effect on the dissolution rate when incorporated into these tablet formulations. Polymers with high molecular weight may act as better binders and promote the retardation of the
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PHARMACEUTICAL TECHNOLOGY Controlle
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3 TABLET MACHINE INSTRUMENTATION IN
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First published in 1991 by ELLIS HO
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7 10 Controlled delivery of theophy
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Slow and steady wins the race Poems
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1 Influence of drug solubility in t
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CH. 1] INFLUENCE OF DRUG SOLUBILITY
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24 MATRIX FORMULATIONS [CH. 2 MATER
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26 MATRIX FORMULATIONS [CH. 2 Fig.
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28 MATRIX FORMULATIONS [CH. 2 Table
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30 MATRIX FORMULATIONS [CH. 2 The e
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34 CH. 3] THE FORMULATION OF SUSTAI
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4 Statistical optimization of a con
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MATRIX FORMULATIONS [CH. 4 45 (4) G
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MATRIX FORMULATIONS [CH. 4 47 Fig.
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Columns 1-4 lead to the matrix of e
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MATRIX FORMULATIONS [CH. 4 51 Table
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MATRIX FORMULATIONS [CH. 4 53 Fig.
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Fig. 5—Linearization of the relea
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58 MATRIX FORMULATIONS [CH. 5 Pevik
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60 MATRIX FORMULATIONS [CH. 5 The d
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6 Controlled release matrix tablets
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CH. 6] CONTROLLED RELEASE MATRIX TA
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7 A new ibuprofen pulsed release or
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CH. 7] A NEW IBUPROFEN PULSED RELEA
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CH. 7] A NEW IBUPROFEN PULSED RELEA
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Page 105 and 106: 104 MULTIPARTICULATES [CH. 9 parace
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Page 133 and 134: 132 CH. 12] BIODEGRADABLE POLYMERS
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Page 143 and 144: 142 CH. 13] A COMPARISON OF DISSOLU
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Page 157 and 158: 156 OPHTHALMIC FORMULATION [CH. 14
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Page 173 and 174: 172 IMPLANTS [CH. 16 The purpose of
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186 CH. 17] SILICON MATRIX SYSTEMS
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194 INDEX dry granulation, 43 elect
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Pharmaceutical Technology: Controlled Drug Release, Volume 2

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