Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Evaluation of the absorption from some commercial sustained-release theophylline products (1980)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 8 (1980), S. 131-149 
    Details
    ISSN: 1573-8744
    Keywords: theophylline ; absorption ; bioavailability ; sustained release ; tablets ; plasma concentrations ; mean plasma concentrations ; steady-state projections
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Absorption of theophylline from three commercial products labeled as sustained release was compared to the absorption from a standard uncoated tablet (Searle 200-mg aminophylline tablet) in a single-dose study. Aminodur tablets (Cooper) and Slophyllin Gyrocap capsules (Dooner) had bioavailability (100.2%±19.8% and 98.5%±13.8%) statistically indistinguishable from that of the standard but showed significantly slower absorption (peak times of 10,4±2.8 and 4.36±1.35 hr) and lower peak plasma concentrations (13.9±4.5 and 22.6±3.5gmg/ml/g dose) than the standard (t peak ,1.52±0.45 hr; Cpeak,28.l±6.2μg/ml/g dose). The time of the plasma concentration peak (2.47±1.38 hr) after a dose of Tedral S.A. (Warner/Chilcott) was not statistically different from that after the standard, but both the peak concentration (16.0±3.9 gmg/ml/g dose) and bioavailability (76.0±18.4%) were. Multiple-dose projections from single-dose data indicate that of the three test products only Aminodur maintains reasonably constant interdose plasma levels during 12 hourly dosing. With an 8 hourly dosing schedule Gyrocaps also might be satisfactory. Reasonable predictions of the plasma concentrations arising from Aminodur doses have been made using a single-compartment body model and assuming input from an outer followed by an inner layer of the tablet. Typically a single dose of a preparation designed for constant release of drug over 12 hr should not produce a plasma concentration plateau in subjects with an average 6.1-hr drug half-life. The apparent plateau in the mean plasma profile (i.e., concentrations at each sampling time averaged over all subjects) for Aminodur doses is evaluated. The interpretation commonly being implied in the publication of mean profiles from bioavailability studies is misleading, particularly when applied to sustained-release preparations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01065189
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Evaluation of the absorption from some commercial enteric-release theophylline products (1980)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 8 (1980), S. 151-164 
    Details
    ISSN: 1573-8744
    Keywords: theophylline ; absorption ; bioavailability ; enteric release ; tablets ; plasma concentrations ; dissolution data
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In a single-dose bioavailability study, Wales, Robinson, Columbia, and Choledyl (Warner/Chilcott) enteric-coated tablets all allowed a bioavailability of theophylline (99%±25%, 102%±23%,103%±18%, and 98%±15%;mean±SD, n=12) statistically indistinguishable from that of the standard uncoated tablet (Searle 200 mg aminophylline). Only the Wales and Choledyl tablets (7.6, 4.2 hr) could be shown (p〈0.05) to generate a peak plasma theophylline concentration later than the standard (1.4 hr). All tablet brands demonstrated a significant lag time before appearance of theophylline in the plasma, and both Wales and Choledyl tablets also had a (t peak -t tag )statistically different from that of the standard. Despite misleading indications from the mean plasma profile (plasma concentrations at each sampling time averaged over all subjects), plasma data from the individual participants and in vitrodissolution data show that, while release of theophylline from the Wales tablet might be inordinately slow, this is not a sustained-release preparation. Of the enteric-coated tablets only the Columbia product allowed significant levels in the first sample after dosage. Five of the 18 Columbia doses gave rise to 40–99%of the peak concentration in the 1- hr sample. In vitro,it takes 39±14 min for 40% of the theophylline content of Columbia tablets to dissolve in simulated intestinal fluid. Surprisingly rapid delivery of an entericcoated tablet to the duodenum would appear to be required to allow a significant percentage of theophylline to be dissolved and absorbed before 1 hr. None of 12 Columbia tablets tested in vitro,however, allowed dissolution of more than 0.2% of their theophylline content during 1 hr immersion in simulated gastric fluid. Since once in intestinal fluid Columbia tablets appear to dissolve more rapidly than the other enteric products, it is not clear whether the five Columbia tablets in question had imperfections or whether, in fact, this tablet brand more closely than the others represents the ideal of immediate release once in the duodenum. Plasma samples should be taken as early as 15 min after dosage when evaluating the bioavailability of enteric release products.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01065190
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Quinidine pharmacokinetics in man: Choice of a disposition model and absolute unavailability studies (1980)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 8 (1980), S. 215-215 
    Details
    ISSN: 1573-8744
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01065195
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Gastrointestinal absorption of quinidine from some solutions and commercial tablets (1980)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 8 (1980), S. 243-255 
    Details
    ISSN: 1573-8744
    Keywords: quinidine ; bioavailability ; absorption ; solutions ; rapidiy releasing tablets ; humans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The gastrointestinal absorption of quinidine from three commercially available tablet products has been compared to that from a quinidine sulfate solution previously found to have 70% of the systematic availability of an intravenous dose. Quinidine gluconate solution was included in the study to compare the absorption characteristics of the two quinidine salts. The tablets were given in a counterbalanced sequence preceded by one quinidine solution and followed by the other in a crossover design. The three tablets proved to be equivalent to one another with respect to extent and rate of absorption. The absorption properties of the two solutions were indistinguishable. The tablets were equivalent to the solutions in extent but not in rate of absorption.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01059645
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Evaluation of the absorption from 15 commercial theophylline products indicating deficiencies in currently applied bioavailability criteria (1980)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 8 (1980), S. 229-242 
    Details
    ISSN: 1573-8744
    Keywords: theophylline ; absorption ; tablets ; oral solution ; intravenous ; bioavailability criteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The biovailability of theophylline from alcoholic and aqueous oral solutions was compared to that from an intravenous dose in 12 normal adults. The alcoholic elixir surprisingly gave rise to a significantly greater (114 ±14%, mean±sd amount absorbed than did the intravenous dose. The aqueous solution (99±8%) and intravenous dose were statistically indistinguishable in this respect, and, furthermore, the extent of absorption from a 300-mg dose of the aqueous solution was 99±10% of that from a 500-mg dose, and not statistically different. The aqueous solution was thus employed in three subsequent studies as a standard with which to compare 13 different types of theophylline tablets, all marketed in the United States. Of the 13 tablets, eight showed bioavailability statistically distinguishable from that of the standard. Nevertheless, for only two tablets could it be claimed with 95% confidence that the bioavailability was less than 95%. For none can it be stated at this confidence level that the bioavailability is less than 90%. Bioavailability studies should include criteria of clinical significance in addition to criteria of statistical significance. Contrary to the usual rationale behind choice of a bioavailability standard, nine of the 12 uncoated tablets appeared to allow more rapid absorption of theophylline than did the standard oral solution, an aqueous syrup. Increasing the dose of syrup decreased the rate of theophylline absorption. Orally administered drug solutions may have properties more absorption rate limiting than the disintegration of many brands of tablet.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01059644
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Effects of Formulation and Food on the Absorption of Hydrochlorothiazide and Triamterene or Amiloride from Combination Diuretic Products (1987)
    Springer
    Pharmaceutical research 4 (1987), S. 348-352 
    Details
    ISSN: 1573-904X
    Keywords: hydrochlorothiazide ; triamterene ; Dyazide ; Maxzide ; amiloride ; Moduretic ; food–drug interactions ; food-formulation interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The absorption of three combination formulations of hydrochlorothiazide and either triamterene or amiloride was studied over a 5-year period in seven separate investigations under varying conditions of food and fasting. The most widely prescribed combination, containing 25 mg of hydrochlorothiazide and 50 mg of triamterene, demonstrated impaired absorption in the fasting state that was partially corrected by the addition of a breakfast high in fat. The increase in the fat content of the food appeared to correlate directly with the amount of both drugs absorbed from this formulation. The second formulation studied, a new combination formulation of 50 mg of hydrochlorothiazide and 75 mg of triamterene, demonstrated acceptable absorption in the fasting state that was not altered by the concurrent administration of a high-fat breakfast. The absorption of the third formulation, a combination of 50 mg hydrochlorothiazide and 5 mg amiloride, was acceptable in the fasting state and demonstrated a slight reduction in the absorption of the amiloride component when administered concurrently with a high-fat meal. The clinical and biopharmaceutic implications of these observations are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1016409606936
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Absence of a significant pharmacokinetic interaction between hydrochlorothiazide and triamterene when coadministered (1984)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 12 (1984), S. 575-586 
    Details
    ISSN: 1573-8744
    Keywords: hydrochlorothiazide ; triamterene ; hydroxytriamterene sulfate ; pharmacokinetics ; bioavailability ; renal clearance ; interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Hydrochlorothiazide, triamterene, and hydroxytriamterene sulfate were monitored in the plasma and urine of 24 healthy young men taking single doses of a liquid preparation containing both hydrochlorothiazide and triameterene, liquid preparations containing either of these drugs alone, and a combination tablet recently formulated with a dose ratio of hydrochlorothiazide: triamterene (1∶1,5) found to give optimal potassium-sparing effect. In contradiction to a recent publication, no interaction between the drugs affecting the bioavailability or renal clearance of either could be demonstrated. The previous report of drug-drug interaction probably arose from formulationrelated problems with bioavailability from the two capsule and two tablet products which had been studied. A well-formulated hydrochlorothiazide-triamterene combination tablet promotes plasma concentrations and urinary excretion of hydrochlorothiazide, triamterene, and hydroxytriamterene sulfate which are virtually identical to those seen after either a combination liquid dosage form or simple liquid forms containing only one of the two drugs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01059553
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    A method for estimating within-individual variability in clearance and in volume of distribution from standard bioavailability studies (1982)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 10 (1982), S. 135-146 
    Details
    ISSN: 1573-8744
    Keywords: theophylline ; intraindividual variability ; within-individual variability ; clearance ; volume
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Bioavailability studies are commonly undertaken, and most, because they involve subjects taking repeated doses of a drug, contain information on intraindividual variability in pharmacokinetics. However, because in such studies bioavailability itself is unknown, it is difficult to resolve which pharmacokinetic parameters vary within individuals. A mathematical model is presented which permits estimation of variability in clearance and in volume of distribution. When applied to pooled data arising from five theophylline bioavailability studies, this model has given statistical evidence that clearance of theophylline is inherently more variable within individuals (coefficient of variation, 13%) than volume of distribution (8%). As a result, use of the measurement AUC ·β rather than AUCas a more precise index of bioavailability is justified in studies where β is measured with reasonable precision. The model could be applied to estimation of withinbatch within-person variability in bioavailability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01062331
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    The impact of neglecting nonlinear plasma-protein binding on disopyramide bioavailability studies (1986)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 14 (1986), S. 365-379 
    Details
    ISSN: 1573-8744
    Keywords: disopyramide ; bioavailability ; protein binding ; nonlinear ; sustained release ; pharmacokinetics ; ultrafiltration ; immunoassay
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Disopyramide has nonlinear protein binding and thus the relationship between the extent of its bioavailability and AUC,the area under the plasma concentration-time curve, is (1) nonlinear and (2) absorption rate-dependent. The unbound species follows linear pharmacokinetics. A solution of disopyramide, the innovator's product, and two generic formulations were found to be statistically indistinguishable in their bioavailability of disopyramide, whether comparison was based upon AUCor area under the plasma unbound concentration-time curve (AUCu).The AUCand AUCugave similar results because of truly similar bioavailability, coupled with sufficiently similar release rates, among the four preparations chosen for study. The concentration dependence of disopyramide protein binding and the time course of unbound plasma concentrations were fit by models which then allowed prediction of AUCunder various biopharmaceutical scenarios. Nonlinear binding of disopyramide to plasma proteins renders AUCan insensitive parameter for the discrimination of products with different extents of bioavailability; immediate release products allowing bioavailabilities of 75 or 125% relative to the solution can generate AUCs86 and 112%, respectively, of that from the solution. Nonlinear binding, furthermore, leads to a tendency for AUC tooverestimate the bioavailability of slower release products in single-dose studies; if AUCwere the index of bioavailability, products permitting the same bioavailability as the solution but releasing over 12 hr could appear to allow 114% relative bioavailability. Moreover, in some situations the bias arising from the insensitivity of AUCto product differences can be reinforced by the dependence of AUCon release rate; an apparent relative bioavailability of 80% can be achieved by a 12-hr release product allowing a true relative bioavailability of a mere 58%. While multiple-dose studies appear largely to avoid the tendency to overestimate low bioavailability in slow-release products, in these studies AUCappears to be even more insensitive in resolving discrepancies between products. Assay technology now available makes AUCua feasible and more reliable index of bioavailability than AUCwhen plasma protein binding of drugs is nonlinear.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01059197
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Divergence in pharmacokinetic parameters of quinidine obtained by specific and nonspecific assay methods (1979)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 7 (1979), S. 303-311 
    Details
    ISSN: 1573-8744
    Keywords: quinidine ; pharmacokinetic parameters ; assay methods ; assay specificity ; area under the plasma concentration-time curve ; bioavailability ; clearance ; therapeutic window
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Previously published estimates of pharmacokinetic characteristics of quinidine can be shown to be dependent on whether the investigators have used analytical methods which are specific for quinidine. Areas under the plasma concentration-time curve and peak plasma concentrations after administration of the drug were higher and clearance values consequently lower in studies utilizing nonspecific assays unable to distinguish quinidine from its metabolites. The error introduced is larger after oral administration as a result of marked first-pass metabolism of quinidine. The absolute oral bioavailabilities from pharmaceutical preparations might therefore be estimated higher in studies with assays including metabolites in the determination. Although the pharmacodynamic response to quinidine is related to the plasma concentration, the therapeutic window of drug concentrations has been defined only using nonspecific assays. In light of the availability of newly developed specific assays, redefinition of the range of therapeutic plasma concentrations is opportune.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01060020
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...