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Christensen JM, Ghannam M, Ayres JW. Neutron activation of iron tablets to evaluate the effects of glycine on iron absorption. J Pharm Sci 1984; 73:1529-31. [PMID: 6520751 DOI: 10.1002/jps.2600731108] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Neutron bombardment (neutron flux, 3 X 10(12) neutrons/cm2/s) of prepared iron tablets containing glycine-iron or iron alone was performed to prepare radioactive tablets to assess the effects of glycine on iron absorption from tableted formulations. No interfering isotopes of sufficient quantity were generated during neutron activation of the iron tablets. Cobalt-60 was the major trace mineral detected and accounted for only 1.3% of the total activity. There may have been trace amounts of zinc-65 or chromium-51 present, but they were not detectable above background radioactivity in the final tablet produced. Iron-59 represented greater than 98% of the radioactivity present in the tablets used in the study. Glycine-containing iron tablets produced dramatically higher amounts of iron in blood and tissues of rabbits (p less than 0.05) than did the same tablet formulations without glycine. The area under the iron blood concentration-time curve over 4 h increased by 67% with glycine added to the formulation over control iron tablets. Iron concentrations in tissues 4 h after iron administration was in the order of blood greater than liver greater than heart greater than kidney greater than muscle.
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27
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Ayres JW, Huang HP, Albert K. Generic tolbutamide tablet dissolution: intralot and interlot variation. J Pharm Sci 1984; 73:1629-34. [PMID: 6520768 DOI: 10.1002/jps.2600731135] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Dissolution profiles for 62 lots of tolbutamide tablets from six manufacturers have been characterized using the USP paddle-stirrer apparatus. Results of paddle-stirrer dissolution for percent drug dissolved at 10, 20, and 30 min correlated well (r2 = 0.7444) with results from the USP rotating-basket test for 39 lots of tolbutamide. Interlot and intralot variability in tolbutamide dissolution was highly dependent on the manufacturer. For one product, the intralot range (for six paddle-stirred tablets) of percent drug dissolved after 30 min was 50-68% while the maximum interlot range for mean dissolution was 58-104%. One lot failed to meet both the rotating-basket and the paddle-stirrer dissolution specifications. Tablet response to aging at 60, 75, and 98% relative humidity over time was also highly manufacturer specific. The innovator's product repeatedly dissolved well when fresh or aged at all humidities. Dissolution from some generic tablets was dramatically depressed by humidity aging, even after only 3 d. Pretreatment of tablets with simulated gastric fluid modified the dissolution profile of one poorly dissolving lot of tablets. Results indicate that manufacturing quality control is highly variable among tolbutamide tablets.
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Abstract
Solutions of each of 10 amino acids or ascorbic acid were mixed with iron and orally administered to rats. Iron was absorbed to a statistically significantly greater extent (p less than 0.05) when mixed with asparagine, glycine, serine, or ascorbic acid as compared with a control solution of iron. The largest effects were for asparagine and glycine, which also increased iron absorption to a significantly greater extent (p less than 0.001) than did serine or ascorbic acid. No statistically significant increase in iron absorption occurred when any of the other amino acids was mixed with iron. The extent of iron absorption from each test solution, as measured by area under the concentration of iron-59 in the blood-time curve (r2 = 0.0002), and the initial rate of iron absorption for each test solution (r2 = 0.01) showed no correlation with the stability constant of the amino acid-iron complex.
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29
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Anderson JL, Ayres JW, Hall CA. Potential pharmacokinetic interaction between theophylline and prednisone. CLINICAL PHARMACY 1984; 3:187-9. [PMID: 6723226] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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30
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Ayres JW. Lot-to-lot variation in dissolution of tolbutamide tablets. AMERICAN JOURNAL OF HOSPITAL PHARMACY 1980; 37:1329-32. [PMID: 7424928] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The dissolution characteristics of tolbutamide tablets made by two manufacturers were compared. Six tablets selected from six lots of each manufacturer were subjected to the USP rotating-basket and paddle-stirrer dissolution tests. Samples were drawn after 10, 20, 30, and 45 minutes for the rotating-basket test and after 10, 20, and 30 minutes for the paddle-stirrer test. Drug concentrations of the dissolution samples were measured by ultraviolet spectroscopy or high-pressure liquid chromatography. All lots passed the disintegration, assay, content uniformity, and tablet weight variation tests; however, there was considerable interlot and intralot variation in the dissolution characteristics of the tablets. The range of interlot differences in the average amount of tolbutamide dissolved using the rotating-basket test was 55.6% for one manufacturer's product and less than 1% for the other's. The ranges were 40.5% and 2.4%, respectively, using the paddle-stirrer test. Similar differences for intralot variation between the two manufacturers' products also existed. Constant patient monitoring appears prudent when products with highly variable dissolution characteristics are used. It is recommended that, for a given patient, the chosen brand of tolbutamide not be changed without careful evaluation.
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31
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Estabrook DR, Stennett DJ, Ayres JW. Stability of uncoated aminophylline tablets in unit dose packages. AMERICAN JOURNAL OF HOSPITAL PHARMACY 1980; 37:1046. [PMID: 7405930] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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32
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Garg DC, Wagner JG, Ayres JW, Albert KS. Determination of adrenal response after oral administration of multiple doses of methylprednisolone. J Clin Pharmacol 1979; 19:644-53. [PMID: 229132 DOI: 10.1002/j.1552-4604.1979.tb01627.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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33
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Gisclon LG, Ayres JW, Ewing GH. Pharmacokinetics of orally administered dyphylline. AMERICAN JOURNAL OF HOSPITAL PHARMACY 1979; 36:1179-84. [PMID: 495617] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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34
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Milsap RL, Ayres JW, Mackichan JJ, Wagner JG. Comparison of two dissolution apparatuses with correlation of in vitro-in vivo data for prednisone and prednisolone tablets. Biopharm Drug Dispos 1979; 1:3-17. [PMID: 552859 DOI: 10.1002/bdd.2510010103] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Dissolution profiles in 0.1N hydrochloric acid using both the paddle stirrer apparatus and the spin filter apparatus were obtained for prednisone tablets made by seven different manufacturers and prednisolone tablets made by eight different manufacturers. Dissolution parameters were correlated with results obtained in three human bioavailability trials which were previously reported. Also, results obtained in one apparatus were correlated with those obtained in the other apparatus. Such correlations may be useful in the setting of in vitro dissolution rate specifications for commerical prednisone and prednisolone tablets.
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35
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Block JH, Levine HL, Ayres JW. Paired-ion reversed-phase high-pressure liquid chromatographic assay of pentobarbital-pyrilamine suppositories. J Pharm Sci 1979; 68:605-8. [PMID: 430500 DOI: 10.1002/jps.2600680524] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The assay of suppositories containing pentobarbital and/or pyrilamine in a water-soluble polyethylene glycol base by high-pressure liquid chromatography is described. No extraction is required. The suppository is dissolved in the mobile phase. This solution is diluted with an internal standard stock solution containing phenobarbital. Chromatographic conditions include a C18 bonded microporous silica column and a mobile phase of 65% 4 x 10(-3) M n-butyl sodium sulfonate in 1% acetic acid and 35% acetonitrile. The procedure using commercial products gave results comparable to those obtained by GLC.
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36
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Stennett DJ, Simonson W, Ayres JW. Effect of membrane filtration on 10-mg/ml cefazolin admixtures. AMERICAN JOURNAL OF HOSPITAL PHARMACY 1979; 36:657-60. [PMID: 453218] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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37
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Baker RW, Tuttle ME, Lonsdale HK, Ayres JW. Development of an estriol-releasing intrauterine device. J Pharm Sci 1979; 68:20-6. [PMID: 758458 DOI: 10.1002/jps.2600680110] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Estriol-releasing intrauterine devices were developed for experimental use in animals and humans. The devices consist of a reservior containing the steroid surrounded by a rate-limiting polyurethane membrane. After an initial transient, the drug is released from the device at a constant rate for 1 year or more; devices with a much longer release period can be fabricated readily. A constant release rate is achieved by maintaining solid drug in the reservoir and good physical contact between the drug and the inside wall of the device. The methods used to fabricate the devices are described along with release rate and stability data.
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38
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Albert KS, Ayres JW, DiSanto AR, Weidler DJ, Sakmar E, Hallmark MR, Stoll RG, DeSante KA, Wagner JG. Influence of kaolin--pectin suspension on digoxin bioavailability. J Pharm Sci 1978; 67:1582-6. [PMID: 712596 DOI: 10.1002/jps.2600671121] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The effect of a kaolin--pectin suspension on the bioavailability of orally administered digoxin was evaluated when both drugs were given concomitantly and when their time of administration was separated by 2 hr. Coadministration of the antidiarrheal with the cardiac glycoside delayed absorption of the latter and, at the same time, decreased by 62% the amount of drug absorbed. Intersubject variation in digoxin bioavailability also was increased more than twofold. When the kaolin--pectin suspension was given 2 hr before the cardiac glycoside, the digoxin absorption rate was not affected, although its relative extent of absorption was reduced by about 20%. In contrast, when the antidiarrheal was given 2 hr after digoxin, neither the rate nor the extent of absorption of the cardiac glycoside was perturbed. No change in the intersubject variability in digoxin bioavailability was noted whether the antidiarrheal was given 2 hr before or 2 hr after the cardiac glycoside.
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39
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Walker RB, Ayres JW, Block JH, Lock A. tert-Butoxycarbanyl as a convenient protecting group in synthesis of potential centrally active dopamine derivatives. J Pharm Sci 1978; 67:558-9. [PMID: 641771 DOI: 10.1002/jps.2600670433] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Several pivaloyl and pivaloyloxy esters and amides of dopamine were synthesized for possible antiparkinson activity. The compounds were synthesized by select O- and N-acylation and N-methylation procedures. The tert-butoxycarbonyl function is an effective and easily removed nitrogen-protecting group for dopamine. Preliminary biological testing results showed that all compounds tested elicited a hypothermic response in mice, while only O,O-dipivaloyl-N,N-dimethyldopamine reversed reserpine-induced motor depression in mice. However, it is difficult to conclude from the preliminary data that the observed biological effects were due to central dopaminergic receptor stimulation.
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40
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Ayres JW, Weidler DJ, MacKichan J, Sakmar E, Hallmark MR, Lemanowicz EF, Wagner JG. Pharmacokinetics of tolmetin with and without concomitant administration of antacid in man. Eur J Clin Pharmacol 1977; 12:421-8. [PMID: 598416 DOI: 10.1007/bf00561061] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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41
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Ayres JW, Weidler DJ, MacKichan J, Wagner JG. Circadian rhythm of urinary pH in man with and without chronic antacid administration. Eur J Clin Pharmacol 1977; 12:415-20. [PMID: 23296 DOI: 10.1007/bf00561060] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
In normal human volunteers, when urinary pH was plotted versus time, the circadian sine-wave type curve was not altered by chronic administration of a commercially available suspension containing a mixture of magnesium and aluminum hydroxides, although the antacid perturbed the entire curve in a more alkaline direction. A single dose of the antacid had little effect on urinary pH. There was a highly significant linear relationship between the change in hydrogen ion concentration during chronic antacid treatment and the initial control urinary hydrogen ion concentration, but there was no significant correlation between change in urinary pH and initial control urinary pH as has been previously reported. The above results were based on the evaluation of the hydrogen ion concentrations of 1562 separate urine samples collected from 24 normal subjects in a three treatment crossover study. It is recommended that: (1) research studies involving drug-drug interactions with antacids be designed to consider the effect of the antacid on the circadian rhythm of urinary pH, and (2) pH values not be averaged as commonly reported in the literature, but rather the pH values be converted to hydrogen ion concentrations before statistical analysis.
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42
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Wagner JG, Ayres JW. Bioavailability assessment: methods to estimate total area (AUC O to infinity) and total amount excreted (A infinity e) and importance of blood and urine sampling scheme with application to digoxin. JOURNAL OF PHARMACOKINETICS AND BIOPHARMACEUTICS 1977; 5:533-57. [PMID: 925886 DOI: 10.1007/bf01061733] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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43
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Garg DC, Ayres JW, Wagner JG. Determination of methylprednisolone and hydrocortisone in plasma using high pressure liquid chromatography. RESEARCH COMMUNICATIONS IN CHEMICAL PATHOLOGY AND PHARMACOLOGY 1977; 18:137-46. [PMID: 905626] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
A method for quantitative determination of methylprednisolone and hydrocortisone in plasma using added methylprednisolone acetate as internal standard and high pressure liquid chromatography is presented. The standard curves were evaluated statistically and logarithmic parabolic equation is preferred over the usual standard curve mathematical relationships. The method was applied to samples of one subject's plasma containing methylprednisolone and endogenous hydrocortisone after oral dosing with multiple doses of methylprednisolone.
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Abstract
The degradation rate of carmustine was investigated in buffered aqueous media at several pH values. The buffering agents studied were those with potential use in parenteral formulations of this drug: acetate, citrate, and phosphate. The apparent first-order degradation rate constants were calculated using a linear regression procedure. A pH range over which minimum degradation occurred was ascertained. General acid and specific base catalysis was demonstrated for the degradation of carmustine. From the data at 5, 22, and 37 degrees, the apparent activation energies for carmustine degradation in buffered aqueous media were computed and were strongly pH dependent.
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45
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Abstract
The degradation rate of carmustine in several solvent mixtures and in mannitol solution was investigated at 5, 22, and 37 degrees. The solvents chosen were those utilized as parenteral diluents. The apparent first-order degradation rate constants were computed using a linear regression procedure. The most nonaqueous solvent mixtures demonstrated minimum apparent degradation rates. The apparent degradation rate constant decreased with a decrease in the macroscopic dielectric constant. From the data at several temperatures, the apparent activation energies for carmustine degradation in the several solvent mixtures were calculated. There was no evidence for a relationship between the apparent activation energy and the dielectric constant.
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46
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Ayres JW, Weidler DJ, Sakmar E, Wagner JG. Linear and nonlinear assessment of tolmetin pharmacokinetics. RESEARCH COMMUNICATIONS IN CHEMICAL PATHOLOGY AND PHARMACOLOGY 1977; 17:583-93. [PMID: 897347] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Plasma concentration-time data in man after oral dosing of the nonsteroidal antiinflammatory agent, tolmetin sodium, were fitted to both linear and nonlinear pharmacokinetic equations. The apparent elimination half-life of tolmetin is shown to be 4.5 to 6.0 hours. An analytical method is presented which allows measurement of plasma concentrations for at least 32 hr (compared with a previous limit of about 8 hr) after a single oral dose of the equivalent of 400 mg of tolmetin acid.
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Abstract
A reproducible and sensitive radioimmunoassay for digoxin in either serum, plasma or urine is described. Using 0.5 ml of serum or plasma, the assay sensitivity is 0.05 ng of digoxin/ml. The antiserum and tracer solutions employed are available in a kit sold in the United States. All other reagents were prepared in the laboratory. The assay allows measurement of digoxin in plasma or serum for 96 hours after single 0.5 mg doses of digoxin; this is necessary in human bioavailability studies to accurately estimate the total area under the digoxin concentration, time curve from zero to infinite time. In contrast, with the kit assay, employing 0.2 ml of plasma or serum, it has been reported that the 12 hr serum digoxin levels, after single 0.5 mg doses, are, in most subjects, below the sensitivity limit (about 0.5 ng/ml) of the assay.
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48
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Ayres JW, Lindstrom FT. Diffusion model for drug release from suspensions I: theoretical considerations. J Pharm Sci 1977; 66:654-62. [PMID: 874746 DOI: 10.1002/jps.2600660513] [Citation(s) in RCA: 39] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
A new mathematical model based on physicochemical principles is presented; it does not require a "diffusion layer" for the release of a suspended drug from a semisolid vehicle. This general model has wide range application to systems where release is controlled by the diffusion rate or dissolution rate of a drug. The appropriate mathematical relationships are derived and evaluated. Theoretical drug concentration distributions in the vehicle and a membrane and the predicted cumulative drug mass uptake by blood under specified conditions are presented. The dissolution rate of solid drug in the vehicle markedly influences predicted drug release using the model presented. It is anticipated that the model will stimulate further research to confirm or reject the assumption that the dissolution rate may be slow enough to be important in the systems studied.
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49
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Tembo AV, Ayres JW, Sakmar E, Hallmark MR, Wagner JG. Plasma prednisolone concentrations: comparison of radioimmunoassay and competitive protein binding assay. Steroids 1977; 29:679-93. [PMID: 898234 DOI: 10.1016/0039-128x(77)90019-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
A comparison was made between plasma concentrations of prednisolone measured by both competitive protein binding radioassay (CPB) and radioimmunoassay (RIA) and, with each assay, using a calibration curve generated from individual subject data and from pooling the individual calibration curva data. The plasma samples were obtained from six normal adult male volunteers who were pretreated with dexamethasone to suppress endogenous hydrocortisone and who then ingested 10 mg of prednisolone. Both the standard curve data and the plasma concentrations were evaluated statistically. It was shown that the CPB method has considerably greater precision than the RIA method and could be employed in bioavailability and pharmacokinetic studies of both prednisolone and prednisone. It was also shown that corticosteroid binding globulin cross-reacts considerably less with the major metabolite of prednisolone, 20beta-dihydroprednisolone, than the particular antiserum used in the RIA.
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50
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Lindstrom FT, Ayres JW. Diffusion model for drug release from suspensions II: release to a perfect sink. J Pharm Sci 1977; 66:662-8. [PMID: 874747 DOI: 10.1002/jps.2600660514] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Numerical mathematical methods are applied to a diffusion model based on physicochemical principles to predict drug release from suspensions of drug in semisolid vehicles. The predicted mass of drug released versus time curves using this model are in agreement with some reported experimental data but differ from predictions using the classical model for semisolid suspensions. The differences are discussed in relation to the drug dissolution rate and diffusion rate in the vehicle.
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