Pharmaceutical Technology: Controlled Drug Release, Volume 2

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MATRIX FORMULATIONS [CH. 3 35 Fig. 1—Potassium chloride release profiles from sustained release matrix tablets (hardness, 7.5–8 kp): 10% (■), 15% (●), 20% (▼) carbomer; 10% (□), 15% (○), 20% methylcellulose. Fig. 2—Potassium chloride release profiles from sustained release matrix tablets (hardness, 7.5–8kp): 10% (■), 15% (●), 20% (▼) polyvinyl chloride; 10% (□), 15% (○), 20% glycerol palmitostearate. RESULTS AND DISCUSSSION Effect of polymer concentration The results of the release experiments are summarized in Fig. 1 and Fig. 2, which represent the percentage released as a function of time. As expected, the drug was released from tablets more slowly with an increase in polymer content. When 10%, 15% and 20% of carbomer were incorporated into the formulations (Fig. 1), the amount of potassium chloride decreased from 93% to 84–7% and 77.3% respectively at the end of 3 h. Glycerol palmitostearate showed similar results for the concentrations of 10%, 15% and 20%, i.e. the amount released was decreased, in 3 h, from 75.7% to 71.4% and 64.9% respectively (Fig. 2). Similar results were also obtained for polyvinyl chloride and methylcellulose. Carbomer and polyvinyl chloride matrix tablets show an
36 CH. 3] THE FORMULATION OF SUSTAINED RELEASE POTASSIUM CHLORIDE TABLETS initial rapid release of potassium chloride. While 52% and 48% of potassium chloride were released from 20% carbomer and polyvinyl chloride formulations, in 1h, only 38% and 39% of potassium chloride were released from formulations containing 20% methylcellulose and glycerol palmitostearate respectively. In order to investigate the mechanism of release, the following semi-empirical equation was used [8]. where Mt/M∞ is the fraction of drug released up to time t, k is a constant incorporating structural and geometric characteristics of the tablet, and n is the diffusional exponent indicative of the mechanism of release. The estimated parameters are given in Table 1. Table 1—Values of constant (k), release exponent (n) and correlation coefficient (r 2 ) following linear regression of dissolution data of formulations containing different polymers (hardness, 7.5–8kp) (1) When equation (1) is applied during the early stages of release (fraction released
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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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90 CH. 8] TOPICAL RELEASE AND PERME
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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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142 CH. 13] A COMPARISON OF DISSOLU
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156 OPHTHALMIC FORMULATION [CH. 14
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162 CH. 15] A SUSTAINED RELEASE OPH
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172 IMPLANTS [CH. 16 The purpose of
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174 IMPLANTS [CH. 16 times with 5 m
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176 IMPLANTS [CH. 16 noted that the
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180 IMPLANTS [CH. 16 Table 3—Tobr
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184 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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