@article {4814,
	title = {NMR imaging investigations of drug delivery devices using a flow-through USP dissolution apparatus},
	journal = {Journal of Controlled Release},
	volume = {68},
	number = {1},
	year = {2000},
	note = {ISI Document Delivery No.: 337YCTimes Cited: 28Cited Reference Count: 11},
	month = {Jul},
	pages = {73-83},
	type = {Article},
	abstract = {A system for performing NMR imaging experiments on drug delivery devices within a how-through dissolution apparatus, USP Apparatus 4, has been developed. The system was used to image the physical changes that occur in solid dosage forms during dissolution in the Row-through apparatus. Simultaneous cumulative drug release measurements were also made. The NMR images obtained under these conditions and the drug release data provide a better understanding of the processes involved in the release of drugs from drug delivery systems based on diffusion, dissolution and osmosis mechanisms. (C) 2000 Elsevier Science B.V. All rights reserved.},
	keywords = {BEHAVIOR, CONTROLLED RELEASE, flow NMR imaging, GEL LAYER, HPMC TABLETS, RELEASE DOSAGE FORMS, USP Apparatus 4},
	isbn = {0168-3659},
	url = {<Go to ISI>://000088390100008},
	author = {Fyfe, C. A. and Grondey, H. and Blazek-Welsh, A. I. and Chopra, S. K. and Fahie, B. J.}
}
@article {4811,
	title = {Quantitative NMR imaging study of the mechanism of drug release from swelling hydroxypropylmethylcellulose tablets},
	journal = {Journal of Controlled Release},
	volume = {68},
	number = {3},
	year = {2000},
	note = {ISI Document Delivery No.: 359DGTimes Cited: 41Cited Reference Count: 14},
	month = {Sep},
	pages = {313-333},
	type = {Article},
	abstract = {NMR imaging has been used to study the release behavior of two model drugs, triflupromazine-HCl and 5-fluorouracil, from swelling hydroxypropylmethylcellulose (HPMC) tablets. Preliminary experiments were performed on equilibrium mixtures of drug, polymer and water to determine how properties such as NMR relaxation parameters and self-diffusion were affected by the drug and polymer concentrations. The tablet swelling was restricted to one dimension and distributions of the water and model drugs were obtained by H-1 and F-19 imaging, respectively. The HPMC distribution at each time in the swelling process was determined indirectly from its effect on the relaxation parameters of the water and the drugs. In the one-dimensional swelling tablet, distributions of drug and polymer were compared to determine what factors influenced the release of drug from the swelling tablet. The distributions for triflupromazine-HCl and HPMC paralleled each other and the drug was only released at the eroding edge of the tablet where the HPMC concentration dropped below 10\%. In contrast, 5-fluorouracil was released much more rapidly from the tablet and appeared to escape by diffusion from regions as high as 30\% HPMC. An empirical measure of the rate of tablet edge movement can be obtained from plots of the edge position as a function of the square root of time. For HPMC, the rate of tablet expansion was determined in this way to be (2.4+/-0.8)x10(-6) cm(2) s(-1). The self-diffusion of triflupromazine-HCl in equilibrated mixtures of similar composition to the eroding tablet edge is similar to 3x10(-6) cm(2) s(-1) while the self-diffusion coefficient of 5-fluorouracil remained higher than this value until the HPMC concentration reached about 30\%. This comparison of {\textquoteright}diffusion{\textquoteright} properties may be useful in predicting the mechanism of drug release from other swelling hydrophilic matrix systems. (C) 2000 Elsevier Science B.V. All rights reserved.},
	keywords = {BEHAVIOR, DOSAGE FORMS, drug release, GEL LAYER, HPMC TABLETS, hydrophilic matrix tablets, hydroxypropylmethylcellulose (HPMC), MATRIX, NMR imaging},
	isbn = {0168-3659},
	url = {<Go to ISI>://000089595800001},
	author = {Fyfe, C. A. and Blazek-Welsh, A. I.}
}
@article {4271,
	title = {Complications in investigations of the swelling of hydrogel matrices due to the presence of trapped gas},
	journal = {Journal of Controlled Release},
	volume = {52},
	number = {1-2},
	year = {1998},
	note = {ISI Document Delivery No.: ZC530Times Cited: 13Cited Reference Count: 11},
	month = {Mar},
	pages = {221-225},
	type = {Article},
	abstract = {In recent studies, NMR imaging has been used to investigate the swelling of hydroxypropylmethylcellulose (HPMC) tablets and to determine polymer concentration distributions in the swollen matrix. The total amount of polymer in the system was computed from these distributions and was up to 35\% greater than the known weight of HPMC in the tablet. This deviation was traced to the presence of air bubbles in the swollen matrix which occupied a significant volume previously assumed to be occupied by polymer and water. When the air in the tablet was removed by vacuum, the swollen gel contained no evidence of air bubbles and the calculated total polymer weights from the HPMC distributions were equal to the amount of HPMC in the tablet. (C) 1998 Elsevier Science B.V.},
	keywords = {BEHAVIOR, CONTROLLED RELEASE, DRUG-RELEASE, GEL, HPMC TABLETS, hydrophilic matrix tablet, hydroxypropylmethylcellulose, IMAGING METHOD, LAYER, MECHANISMS, NMR imaging, RELEASE DOSAGE FORMS, swelling},
	isbn = {0168-3659},
	url = {<Go to ISI>://000072589600022},
	author = {Fyfe, C. A. and Blazek, A. I.}
}
