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1

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In Vitro Adsorption of Bile Salts by Colestipol Hydrochloride (1989)

Konechnik, Thomas J. ; Kos, Rosemary ; White, Joe L. ; [et al.]

Springer

Pharmaceutical research 6 (1989), S. 619-623

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ISSN: 1573-904X

Keywords: colestipol hydrochloride ; bile salt adsorption ; internal surface area ; anion-exchange copolymer

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology

Notes: Abstract The acid–base titration of colestipol hydrochloride exhibits no sharp inflection points, indicating a weakly basic anion-exchange copolymer. The swelling of colestipol hydrochloride in water and the adsorption of cholate anion are inversely related to pH and are, therefore, related to the ionization state of the copolymer. The Langmuir adsorption parameters at pH 7.5 and 37°C are similar for cholate, glycocholate, and taurocholate anions. Adsorption capacity was not related to particle size and exceeded the adsorptive capacity of the external surface by three orders of magnitude. Therefore, it is believed that the swelling of colestipol hydrochloride makes extensive internal surface area available for adsorption of bile salts. The rate of adsorption depends on the concentration of sodium cholate to which the colestipol hydrochloride is exposed. Adsorption was complete within 5 min when the concentration was below the adsorptive capacity. In contrast, adsorption at levels of sodium cholate at or above the adsorptive capacity was not complete within a 3-hr test period.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1015961700383

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2

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Effect of Anions on Adsorption of Bile Salts by Colestipol Hydrochloride (1989)

Bilicki, Christine V. ; White, Joe L. ; Hem, Stanley L. ; [et al.]

Springer

Pharmaceutical research 6 (1989), S. 794-797

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ISSN: 1573-904X

Keywords: colestipol hydrochloride ; bile salt adsorption ; competitive adsorption

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology

Notes: Abstract The Langmuir affinity constant and adsorptive capacity for the adsorption of citrate anion or cholate anion by colestipol hydrochloride at pH 7.5, 37°C, were similar. Prior exposure of colestipol hydrochloride to citrate anion caused the adsorption of cholate anion to decrease slightly in comparison to a control utilizing only cholate anion. The concentration of citrate anion was found to be directly related to the decrease in cholate anion adsorption. Simultaneous exposure of colestipol hydrochloride to citrate and cholate anions at pH 7.5, 37°C, resulted in the same adsorption of cholate anion as sequential exposure to citrate anion followed by cholate anion. Sequential exposure of colestipol hydrochloride to simulated gastric fluid and simulated intestinal fluid containing cholate anion resulted in a small decrease in cholate adsorption which was attributed to competition with phosphate anion in simulated intestinal fluid. Pepsin in the simulated gastric fluid did not affect adsorption of cholate anion from simulated intestinal fluid. Preexposure to components of tomato juice and orange juice also slightly reduced the adsorption of cholate anion by colestipol hydrochloride.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1015979631759

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3

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In Vitro and in Vivo Evaluation of Whole and Half Tablets of Sustained-Release Adinazolam Mesylate (1991)

Skoug, John W. ; Borin, Marie T. ; Fleishaker, Joseph C. ; [et al.]

Springer

Pharmaceutical research 8 (1991), S. 1482-1488

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ISSN: 1573-904X

Keywords: adinazolam mesylate ; oral sustained release ; matrix sustained release ; mechanism ; in vivo/in vitro correlation ; bioavailability ; absorption

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology

Notes: Abstract The mechanism of release from sustained-release adinazolam mesylate tablets was assessed by the Higuchi equation and by analysis of drug release profiles through 60% released using the Peppas equation. Computed values of the diffusional exponent, n, ranged from 0.59 to 0.66. Values of n in this range are consistent with a mixed mechanism of release, with diffusion of drug through the hydrated polymer matrix and relaxation of this matrix being the principal processes controlling release. The rate of in vitro drug release was increased for half tablets relative to whole tablets and is attributed to an increase in the surface to volume ratio of half tablets of about 16%. This increase in surface-to-volume ratio of half tablets was reflected by an increase in the constant, k, from the Peppas equation of 20–23% and by an increase in the slope of Higuchi plots of 12–18% for four lots of tablets. In vivo/in vitro relationships from two bioavailability studies were thoroughly evaluated. Using either a linear or a quadratic relationship, an in vivo/in vitro correlation exists for sustained-release adinazolam mesylate tablets.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1015834114359

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4

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The Effect of Food on Gastrointestinal (GI) Transit of Sustained-Release Ibuprofen Tablets as Evaluated by Gamma Scintigraphy (1990)

Borin, Marie T. ; Khare, Subhash ; Beihn, Robert M. ; [et al.]

Springer

Pharmaceutical research 7 (1990), S. 304-307

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ISSN: 1573-904X

Keywords: scintigraphy ; neutron activation ; bioavailability ; ibuprofen ; sustained release ; food effect ; gastrointestinal transit

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology

Notes: Abstract The GI transit of radiolabeled sustained-release ibuprofen 800-mg tablets in eight healthy, fed volunteers was monitored using external gamma scintigraphy. Ibuprofen serum concentrations were determined from blood samples drawn over 36 hr following dosing. Sustained-release ibuprofen tablets containing 0.18% of 170Er2O3 (〉96% 170Er) in the bulk formulation were manufactured under pilot-scale conditions and were radiolabeled utilizing a neutron activation procedure which converted stable 170Er to radioactive 171Er (t 1/2 = 7.5 hr). At the time of dosing, each tablet contained 50 µCi of 171Er. Dosage form position was reported at various time intervals. In five subjects the sustained-release tablet remained in the stomach and eroded slowly over 7–12 hr, resulting in gradual increases in small bowel radioactivity. In the remaining three subjects, the intact tablet was ejected from the stomach and a gastric residence time of approximately 4 hr was measured. This is in marked contrast to a previous study conducted in fasted volunteers in which gastric retention time ranged from 10 to 60 min. Differences in GI transit between fed and fasted volunteers had little effect on ibuprofen bioavailability. AUC and T max were unaltered and C max was increased by 24%, which is in agreement with results from a previous, crossover-design food effect study.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1015842600189

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5

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Effect of Competing Anions on Binding of Bile Salts by Cholestyramine (1991)

Kos, Rosemary ; White, Joe L. ; Hem, Stanley L. ; [et al.]

Springer

Pharmaceutical research 8 (1991), S. 238-241

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ISSN: 1573-904X

Keywords: cholestyramine ; bile salt binding ; competitive binding

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology

Notes: Abstract The binding of bile salts by cholestyramine may be influenced by other anions, as the Langmuir adsorption coefficients for three bile salts tested were similar to the model anion, citrate. However, the selectivity coefficient indicated preferential binding of cholate anion in comparison to citrate anion. Binding experiments confirmed cholestyramine's preference for bile salts as the presence of other anions reduced but did not prevent the binding of cholate anion. Binding of cholate anion was reduced in direct relationship to the citrate anion concentration. Prior exposure of cholestyramine to citrate anion caused the binding of cholate anion to decrease slightly. Sequential exposure of cholestyramine to simulated gastric fluid and simulated intestinal fluid containing cholate anion resulted in a decrease in cholate binding which was attributed to competition with anions present in the gastrointestinal fluids. Components of tomato juice and orange juice, fluids commonly used to enhance ingestion of cholestyramine, also reduced the binding of cholate anion.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1015804423194

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6

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Species-dependent enantioselective pharmacokinetics of PNU-103017, a Pyrone HIV protease inhibitor (1998)

Zhong, Wei-Zhu ; Williams, Marta G. ; Borin, Marie T. ; [et al.]

New York, NY [u.a.] : Wiley-Blackwell

Chirality 10 (1998), S. 210-216

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ISSN: 0899-0042

Keywords: enantiospecific assay ; rat ; dog ; human ; enantiomer disposition ; HIV protease inhibitor ; Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: PNU-103017, 4-Cyano-N-(3-(cyclopropyl(5,6,7,8,9,10-hexahydro-4-hydroxy-2-oxo-2H-cycloocta(b) pyran-3-yl)methyl)phenyl)-benzenesulfonamide, is a selective HIV aspartyl protease inhibitor under evaluation as a potential oral treatment of Acquired Immunodeficiency Diseases. PNU-103017 is a racemic mixture of two enantiomers, designated PNU-103264 (R-) and PNU-103265 (S-). Stereoselective pharmacokinetics of the two enantiomers of PNU-103017 were observed in the dog, rat, and human after single and multiple dose administration of the racemate and were apparently species-dependent. Mean enantiomeric ratios of plasma concentrations (R-/S-) at each time point were greater than 1 in the dog, ranging from 1.22 to 3.06, but less than 1 in the rat and in the human, ranging from 0.44 to 0.80 and 0.23 to 0.73, respectively. A trend towards increased or decreased (farther from 1:1, R-/S-) enantiomeric ratio of plasma concentrations with time after each administration was also observed. The enantiomeric ratio remained unchanged after multiple dose administration in the rat, dog, and human although enzyme induction and increased plasma clearance were observed for both enantiomers. Chirality 10:210-216, 1998. © 1998 Wiley-Liss, Inc.

Additional Material: 6 Ill.

Type of Medium: Electronic Resource

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