Pharmaceutical Technology: Controlled Drug Release, Volume 2

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IMPLANTS [CH. 17 189 Fig. 4—Weight change (% (w/w)) during Gly-Tyr release from PDMS matrices (matrix excipient HEC, viscosity grade 300 mPas) for the following matrix loadings (w/w): ∆, 30%; 35%; ◊, 40%; □, 50% . Mean values, n=3. Fig. 5—Weight change (% (w/w)) during Gly-Tyr release from PDMS matrices containing HEC (matrix loading 30% (w/w)). Viscosity grade of HEC were 300 (●), 6000 (∆), and 30 000 (▲) mPas. Mean values, n=3. These observations suggest that a prerequisite for getting long-term drug release and release and release exponents above 0.5 is long-term retention of the excipient within the pores. Obvously, the hydrated, hydrocolloid-type excipients in the matrix pores act as diffusion medium for the drug. In the case of a high dissolution rate of excipient and/or high matrix loading, strong initial swelling, rapid depletion of matrix excipient and consequently depletion of the elastic matrix pores occur. This should lead to curved release plots. It is noteworthy that swelling maxima have no influence on release profiles; obviously, therefore, excipient is released from zones of the matrix already drug depleted.
190 CH. 17] SILICON MATRIX SYSTEMS FOR LONG-TERM CONSTANT RELEASE OF PEPTIDES Fig. 6—Weight change (% (w/w)) during Gly-Tyr release from PDMS matrices containing BSA. Quickly dissolving BSA: matrix loadings (w/w) of 40% (○) and 50% . Slowly dissolving BSA: Loadings (w/w) of 30% (∆), 40% (◊), 50% (□). Mean values, n=3. Table 3—Residual amount of excipient and water content of remaining excipient in matrix after 16 days of release On the other hand, when the excipient is leached out slowly, long-term swelling within the pores obviously contributes to time-dependent changes of parameters from equation (1). This may lead to release exponents exceeding the value of 0.5. The diffusion coefficient D may increase on swelling [18]; as shown in Table 2 and Fig. 2, a suitable viscosity grade is essential for convenient
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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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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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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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90 CH. 8] TOPICAL RELEASE AND PERME
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104 MULTIPARTICULATES [CH. 9 parace
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108 MULTIPARTICULATES [CH. 9 Fig. 2
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118 CH. 10] CONTROLLED DELIVERY OF
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126 CH. 11] THE EFFECT OF FOOD ON G
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128 CH. 11] THE EFFECT OF FOOD ON G
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132 CH. 12] BIODEGRADABLE POLYMERS
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Pharmaceutical Technology: Controlled Drug Release, Volume 2

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