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  • clearance  (1)
  • disposition rate constant  (1)
  • intramuscular  (1)
  • mean plasma concentrations  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    Intraindividual variability in theophylline pharmacokinetics: Statistical verification in 39 of 60 healthy young adults (1982)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 10 (1982), S. 123-134 
    Details
    ISSN: 1573-8744
    Keywords: theophylline ; pharmacokinetics ; variability ; disposition rate constant ; man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract After administering a single 300 mg dose of theophylline in oral solution to 12 healthy adults, the dose-normalized area under the plasma concentration-time curve was 97.2±20.1 % (mean±SD) of that after giving a 500 mg dose and statistically indistinguishable. Similarly, these areas multiplied by the individual's terminal disposition rate constant (β) were statistically indistinguishable between 300 and 500mg doses (99.1±10.3%), giving no evidence of dose-dependence for theophylline kinetics at the levels below 15 μg/ml observed in these individuals. After an intravenous dose, a shortlived distribution phase (t1/2α) is sometimes seen. An a phase, however, is hardly discernible in over 250 profiles arising from oral doses administered during five single dose bioavailability studies. Almost all such profiles appear to follow single-compartment model predictions. With precautions to avoid a potential a phase, a terminal log-linear slope can be fitted by least squares analysis with a relative standard error in the slope determination almost always less than 6%. Covariance analysis confirms statistically that 39 of the 60 participating individuals varied in their β on the different occasions each was required to take a dose during the course of a crossover bioavailability trial. In one study, even though each individual was observed on only two occasions, 9 out of 12 showed statistically identifiable variation in β. Fluctuations in β of 60% can be seen. Changes of 30% or greater are common and can occur within 3 or 4 days. Thus real, large, and potentially frequent changes in β of theophylline have been identified in a majority of normal subjects. These changes do not appear to be confined to either sex, to smokers or nonsmokers, or to heavier or lighter individuals. No chronological pattern has, as yet, been recognized in the intraindividual variability in β.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01062330
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    Paper (German National Licenses)
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  • 2
    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
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    Paper (German National Licenses)
    Fulltext
  • 3
    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
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    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Route of Administration and Sex Differences in the Pharmacokinetics of Aspirin, Administered as Its Lysine Salt (1989)
    Springer
    Pharmaceutical research 6 (1989), S. 660-666 
    Details
    ISSN: 1573-904X
    Keywords: aspirin ; pharmacokinetics ; intramuscular ; sex differences ; rate of absorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract One thousand milligrams of aspirin, as its lysine salt, was administered intravenously, orally, and intramuscularly to nine male and nine female young healthy adult volunteers. After intravenous injection mean (±SD) values of clearance, steady-state volume of distribution, and terminal half-life were 12.2 ± 2.2 ml/min/kg, 0.219 ± 0.042 liter/kg, and 15.4 ± 2.5 min, respectively, with no differences between males and females. Following oral administration aspirin was absorbed more quickly in females than in males (mean absorption times of 16.4 and 21.3 min, respectively) although the bioavailability, 54%, was the same in both groups. In contrast, following intramuscular administration, aspirin was absorbed more slowly in females than males (mean absorption times of 97 and 53 min, respectively) but again the bioavailability, 89%, was the same in both groups. The data suggest that in the female the intramuscular injection is going into fat. Salicylic acid concentration–time profiles showed a less pronounced sex difference and were comparable among the three routes of administration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015978104017
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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