Pharmaceutical Technology: Controlled Drug Release, Volume 2

More documents

Recommendations

Info

CH. 9] POLYACRYLATE (EUDRAGIT RETARD) MICROSPHERES 113 Table 3—Effect of initial nifedipine concentration on microsphere drug content a a Microspheres were prepared using 11 of 0.8% ppolyvinyl alcohol solution and 25 g Eudragit RSS:RL mixture (1:1) in 80 ml of methylene chloride stirred at 400 rev/min. b Mean values of duplicates. c As in Table 1. structure of the nifedipine microsphere which showed rippled and rough surfaces (Fig. 8). Also, nifedipine crystals were observed not to be attached firmly to the surface structure of the nifedipine microspheres. This phenomenon could be attributed to possible molecular interactions between the coating polymer and the nifedipine in that an excess of incorporated drug might result in recrystallization of nifedipine within the microspheres. This was further supported by the lack of any thermal event during the differential scanning calorimetry analysis of these microspheres. Incorporation of increasing amounts of nifedipine within the microspheres gradually augmented their mean diameter and particle size distribution (Fig. 9). It could be observed that, in spite of a large degree of overlap in the particle size of the microspheres prepared using either the low or the high initial drug concentration, there was a clear tendency towards particle size increase with increasing nifedipine concentration. A similar behaviour was noted in the corresponding calculated mean diameters: 397±92, and 386±104 µm for microspheres with drug contents of 4. 8% and 9.1% respectively, and 546±201 and 599±183 µm for nifedipine-loaded microspheres having payloads of 16.6% and 31% (w/w) respectively. CONCLUSION It appeared that the experimental conditions used in the present study favoured the formation of microspheres of a new type which could be defined as ‘film-type’ microspheres. They consisted of spherical micromatrices comprising an internal void space and a polymeric membrane of variable thickness where the drug is dispersed in either a molecular or a solid state depending on the payload.
114 MULTIPARTICULATES [CH. 9 Fig. 8—Scanning electron micrograph of Eudragit microspheres containing (a) 14.3% nifedipine and (b) 18.8% nifedipine at various magnifications. For experimental conditions see Fig. 1. Fig. 9—Cumulative frequency plot of nifedipine-Eudragit microspheres as a function of the initial nifedipine concentration. Microspheres were prepared using 1 1 of 0.8% PVA and 25 g of Eudragit RS:RL mixture (1:1) in 80 ml of methylene chloride stirred at 400 rev/min.
Page 2 and 3:
PHARMACEUTICAL TECHNOLOGY Controlle
Page 4 and 5:
3 TABLET MACHINE INSTRUMENTATION IN
Page 6 and 7:
First published in 1991 by ELLIS HO
Page 8 and 9:
7 10 Controlled delivery of theophy
Page 10:
Slow and steady wins the race Poems
Page 14 and 15:
1 Influence of drug solubility in t
Page 16 and 17:
CH. 1] INFLUENCE OF DRUG SOLUBILITY
Page 18 and 19:
Page 20 and 21:
Page 22:
Page 25 and 26:
24 MATRIX FORMULATIONS [CH. 2 MATER
Page 27 and 28:
26 MATRIX FORMULATIONS [CH. 2 Fig.
Page 29 and 30:
28 MATRIX FORMULATIONS [CH. 2 Table
Page 31 and 32:
30 MATRIX FORMULATIONS [CH. 2 The e
Page 33 and 34:
32 MATRIX FORMULATIONS [CH. 2 Table
Page 35 and 36:
34 CH. 3] THE FORMULATION OF SUSTAI
Page 37 and 38:
Page 39 and 40:
Page 41 and 42:
Page 44 and 45:
4 Statistical optimization of a con
Page 46 and 47:
MATRIX FORMULATIONS [CH. 4 45 (4) G
Page 48 and 49:
MATRIX FORMULATIONS [CH. 4 47 Fig.
Page 50 and 51:
Columns 1-4 lead to the matrix of e
Page 52 and 53:
MATRIX FORMULATIONS [CH. 4 51 Table
Page 54 and 55:
MATRIX FORMULATIONS [CH. 4 53 Fig.
Page 56:
Fig. 5—Linearization of the relea
Page 59 and 60:
58 MATRIX FORMULATIONS [CH. 5 Pevik
Page 61 and 62:
60 MATRIX FORMULATIONS [CH. 5 The d
Page 63 and 64: 62 MATRIX FORMULATIONS [CH. 5 Fig.
Page 67 and 68: 66 MATRIX FORMULATIONS [CH. 5 Table
Page 72 and 73: 6 Controlled release matrix tablets
Page 74 and 75: CH. 6] CONTROLLED RELEASE MATRIX TA
Page 80 and 81: 7 A new ibuprofen pulsed release or
Page 82 and 83: CH. 7] A NEW IBUPROFEN PULSED RELEA
Page 88: CH. 7] A NEW IBUPROFEN PULSED RELEA
Page 91 and 92: 90 CH. 8] TOPICAL RELEASE AND PERME
Page 101 and 102: 100
Page 103 and 104: 102
Page 105 and 106: 104 MULTIPARTICULATES [CH. 9 parace
Page 107 and 108: 106 MULTIPARTICULATES [CH. 9 (a) th
Page 109 and 110: 108 MULTIPARTICULATES [CH. 9 Fig. 2
Page 111 and 112: 110 MULTIPARTICULATES [CH. 9 Fig. 6
Page 113: 112 MULTIPARTICULATES [CH. 9 Fig. 7
Page 117 and 118: 116
Page 119 and 120: 118 CH. 10] CONTROLLED DELIVERY OF
Page 127 and 128: 126 CH. 11] THE EFFECT OF FOOD ON G
Page 129 and 130: 128 CH. 11] THE EFFECT OF FOOD ON G
Page 131 and 132: 130
Page 133 and 134: 132 CH. 12] BIODEGRADABLE POLYMERS
Page 141 and 142: 140
Page 143 and 144: 142 CH. 13] A COMPARISON OF DISSOLU
Page 153 and 154: 152
Page 155 and 156: 154
Page 157 and 158: 156 OPHTHALMIC FORMULATION [CH. 14
Page 163 and 164: 162 CH. 15] A SUSTAINED RELEASE OPH
Page 165 and 166:
164 CH. 15] A SUSTAINED RELEASE OPH
Page 167 and 168:
Page 169 and 170:
Page 171 and 172:
170
Page 173 and 174:
172 IMPLANTS [CH. 16 The purpose of
Page 175 and 176:
174 IMPLANTS [CH. 16 times with 5 m
Page 177 and 178:
176 IMPLANTS [CH. 16 noted that the
Page 179 and 180:
178 IMPLANTS [CH. 16 Fig. 1—The e
Page 181 and 182:
180 IMPLANTS [CH. 16 Table 3—Tobr
Page 183 and 184:
182
Page 185 and 186:
184 CH. 17] SILICON MATRIX SYSTEMS
Page 187 and 188:
Page 189 and 190:
Page 191 and 192:
Page 193 and 194:
192
Page 195 and 196:
194 INDEX dry granulation, 43 elect
show all

Pharmaceutical Technology: Controlled Drug Release, Volume 2

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?