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  • Chemistry  (16,939)
  • Polymer and Materials Science  (7,390)
  • Biochemistry and Biotechnology  (893)
  • pharmacokinetics  (172)
  • Wiley-Blackwell  (17,495)
  • Springer  (173)
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  • 2020-2024
  • 1990-1994  (10,647)
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  • 1993  (10,647)
  • 1980  (7,021)
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  • 2020-2024
  • 1990-1994  (10,647)
  • 1980-1984  (7,021)
  • 1975-1979
  • 1940-1944
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular evolution 15 (1980), S. 79-101 
    ISSN: 1432-1432
    Keywords: Molecules ; Interstellar ; Chemistry ; Isotopes ; Solar system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The study of interstellar molecules broadly includes two areas of interest. One area uses the unique ability of molecules to act as probes of the physical conditions in the cold, dense, visually opaque component of the interstellar medium. The physical properties of this and other components of the interstellar medium are summarized. The other area deals with the chemistry of interstellar molecules, recent aspects of which are emphasized in this review. Gas-phase chemistry, shock chemistry, and grain surface chemistry are discussed in the context of recent observations. No present observations suggest that surface reactions are relevant, but neither can they be ruled out. Ion-molecule reactions are clearly operative, at least for the simpler species. Chemical isotope fractionation is reviewed, andd it is concluded that the complexities of the chemistry allow no cosmological conclusions to be drawn from observations of deuterium in interstellar molecules, while the presence of13C in interstellar molecules permits an estimate of the12C/13C ratio which is consistent with the current concepts of the nucleosynthesis history of the Galaxy. Possible connections between interstellar molecules and the early molecular history of the solar system are discussed.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Pure and applied geophysics 118 (1980), S. 128-151 
    ISSN: 1420-9136
    Keywords: Galactic cosmic rays ; Solar proton events ; Particle precipitation ; Chemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract An assessment is made of the relative contribution of certain classes of energetic particle precipitation to the chemical composition of the middle atmosphere with emphasis placed on the production of odd nitrogen and odd hydrogen species and their subsequent role in the catalytic removal of ozone. Galactic cosmic radiation is an important source of odd nitrogen in the lower stratosphere but since the peak energy deposition occurs below the region where catalytic removal of O3 is most effective, it is questionable whether this mechanism is important in the overall terrestrial ozone budget. The precipitation of energetic solar protons can periodically produce dramatic enhancement in upper stratospheric NO. The long residence time of NO in this region of the atmosphere, where catalytic interaction with O3 is also most effective, mandates that this mechanism be included in future modelling of the global distribution of O3. Throughout the mesosphere the precipitation of energetic electrons from the outer radiation belt (60°≲Λ≲70°) can sporadically act as a major local source of odd hydrogen and odd nitrogen leading to observable O3 depletion. Future satellite studies should be directed at simultaneously measuring the precipitation flux and the concomitant atmosphere modification, and these results should be employed to develop more sophisticated models of this important coupling.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1041
    Keywords: Liver cirrhosis ; Spirapril ; ACE inhibitor ; pharmacokinetics ; haemodynamic effects ; liver function tests
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics and haemodynamic effects of orally administered spirapril, a novel angiotensinconverting enzyme (ACE) inhibitor, have been investigated in patients with liver cirrhosis (n=10), in patients with chronic, non-cirrhotic liver disease (n=8) and in a control group of healthy subjects (n=16). The absorption and elimination of spirapril did not differ between patients with liver disease and control subjects. In contrast, the bioavailability of spiraprilat, the metabolite responsible for the pharmacological action of spirapril, was significantly reduced in patients (AUC 820 μg·h·l−1, 923 μg·h·l−1 and 1300 μg·h·l−1 in patients with cirrhosis, patients with non-cirrhotic liver disease and in healthy subjects, respectively. Compared to healthy subjects, cirrhotic patients had a reduced rate constant of spiraprilat formation (1.10 h−1 in patients vs. 2.00 h−1 in control subjects) while the elimination half-life of spiraprilat was not different. The effect of spirapril on diastolic blood pressure was decreased in patients with chronic liver disease as compared to the controls. Thus, the pharmacokinetics of spirapril was unchanged in patients with different types of liver disease, including cirrhosis. However, the bioavailability of spiraprilat and hypotensive effect of spirapril were reduced in patients.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 45 (1993), S. 357-361 
    ISSN: 1432-1041
    Keywords: Circadian rhythms ; Indomethacin ; Ketoprofen ; pharmacokinetics ; time-varying models ; nonsteroidal anti-inflammatory drugs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary A one-compartment model with first-order absorption has provided good fits to five sets of indomethacin data and four sets of ketoprofen data taken at different times of day. There was substantial variation in the model parameters with time of administration and most of the features of this variation applied equally to both drugs. From the data examined, the source of variation appears to be mainly in the absorption phase and this was confirmed using a chronokinetic analysis, in which simultaneous fits were obtained with time-variant rate parameters. However, there may also be circadian variation in protein binding. The danger of quoting parameter values for either of these two drugs based on administration at a single time of day has been illustrated, and this may well be true for other drugs.
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  • 5
    ISSN: 1432-1041
    Keywords: Gamma-hydroxybutyric acid ; pharmacokinetics ; dose-proportionality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Gamma-hydroxybutyric acid (GHB) is effective in treatment of the alcohol and opiate withdrawal syndromes. Its absorption and disposition kinetics have been studied in 8 healthy male volunteers following oral administration of single doses of 12.5, 25 and 50 mg kg−1. The AUC increased disproportionately with the dose and so the apparent oral clearance decreased significantly as the dose was increased, whereas the terminal half-life and mean residence time increased. The peak plasma concentrations normalised to the lowest dose fell significantly with increasing doses, whilst the corresponding peak times increased. These findings suggest that both the oral absorption and the elimination of GHB are capacity-limited processes. GHB did not bind to significant extent to plasma proteins over the therapeutic concentration range. The pharmacokinetic parameters in healthy volunteers were not significantly different from those previously observed in alcohol-dependent patients with compensated alcoholic liver disease.
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  • 6
    ISSN: 1432-1041
    Keywords: Glyceryl trinitrate spray ; pharmacokinetics ; a/b-ratio ; pulmonary artery diastolic pressure ; finger pulse curve ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The time course and the magnitude of the effect of glyceryl trinitrate (GTN) on central venous (pulmonary artery diastolic pressure-PAPd) and peripheral arterial (a/b-ratio of the finger pulse wave) haemodynamics were compared in a randomized double-blind cross-over study in 12 patients suffering from congestive heart failure (NYHA II–III) with elevated PADd at rest (≥15 mm Hg). The data were obtained in a bioavailability study of two sprays of glyceryl trinitrate, which differed in their galenical characteristics and in the dose of GTN (0.4 mg vs. 0.8 mg). Following sublingual administration of each spray, PAPd, a/b-ratio and the plasma concentrations of GTN and its metabolites were measured up to 30 min. The relative bioavailability of GTN of the test preparation was estimated to be 157%, 161% and 147%, when calculated from the plasma concentration-time data or the integrated effect of GTN on a/b-ratio or PAPd, respectively. The mean time courses of the decrease in PAPd and the increase in the a/b-ratio of the finger pulse curve were mirror images. Thus, there was a strong correlation between the mean values of PAPd and a/b-ratio following the administration of glyceryl trinitrate. Since the slope of the relationship differed considerably between the patients, the magnitude of effect of GTN on PAPd in the individual patient could not be predicted from the changes in a/b-ratio.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 44 (1993), S. 463-466 
    ISSN: 1432-1041
    Keywords: Benazepril ; Proteinuria ; benazeprilat ; ACE inhibitor ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary We have investigated whether the pharmacokinetics and pharmacodynamics of the ACE inhibitor benazepril hydrochloride are altered with proteinuria by studying 8 patients with major proteinuria of different causes who were given a single dose of 10 mg p.o. The maximum plasma concentration of benazepril was found between 0.5 and 2 h after dosing (median 1 h). Its elimination was almost complete within 6 h. Peak plasma levels of benazeprilat, the active metabolite of benazepril, were observed between 1 and 6 h (median 2.5 h). The elimination of benazeprilat from plasma was biphasic, with mean initial and terminal half-lives of 3.0 and 17.3 h, respectively. On average, the pharmacokinetic parameters of benazepril and benazeprilat in the patients did not differ from those in a historical control group of healthy volunteers, but intersubject variability in the AUC and half-lives of benazeprilat was greater in the patients. Plasma ACE was completely inhibited from 1.5 to 6 h after dosing, and at 48 h the mean inhibition was still 42 %. Plasma renin showed substantial intersubject variation. Mean supine blood pressure (systolic/diastolic) was reduced from baseline by a maximum of 18/13 mm Hg at 6 h. Proteinuria was diminished after benazepril in 7 patients. In conclusion, the results of this study suggest that proteinuria in the nephrotic range does not require a change in benazepril dosage.
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  • 8
    ISSN: 1432-1041
    Keywords: dDAVP ; bioavailability ; gastrointestinal tract ; healthy volunteers ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The absolute bioavailability of an aqueous solution of 1-deamino-8-D-arginine vasopressin (dDAVP) from different regions of the gastrointestinal (GI) tract (stomach, duodenum, jejunum, ileum, colon, rectum) has been studied in 6 healthy, male volunteers aged 24 to 35 years, followed for 12 h after each drug administration. For i. v. administration the subjects received 4 μg dDAVP. For intestinal administration 400 μg dDAVP was directly applied to six distinct sites in the GI tract via two or four channel tubes with or without a distal occlusive balloon. Biological effects were assessed and plasma and urinary levels of dDAVP were measured using a specific, sensitive RIA. Urine osmolality remained elevated and diuresis decreased for 12 h following dDAVP administration irrespective of the site of application. After i. v. administration, the half-life of elimination of dDAVP was 60.0 min, plasma clearance 1.7 ml·min−1·kg−1, amount excreted in urine 2.0 μg and renal clearance was 0.8 ml·min−1·kg−1. The mean bioavailability (f) after gastric application was 0.19% (range 0.02–0.35%). f was 0.24% after duodenal application (range 0.04–0.62%), 0.19% after jejunal (range 0.01–0.41%), 0.03% after distal ileal (range 0.01–0.08%), 0.04% after proximal colonic (range 0.01–0.12%) and 0.04% after rectal (0.01–0.10%) application. The bioavailability was significantly higher in the three upper GI regions in comparison to the three lower regions. The bioavailability of dDAVP after gastric, duodenal and jejunal application was similar to that after swallowing a tablet in a previous study. Absorption from the ileum was lower than expected and no preferential site of absorption was found.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 44 (1993), S. 247-251 
    ISSN: 1432-1041
    Keywords: Proguanil ; Pregnancy ; Malaria ; cycloguanil ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Plasma and whole blood concentrations of proguanil, its active metabolite cycloguanil, and the inactive metabolite 4-chlorophenyl-biguanide, were measured by HPLC in 10 healthy Karen women in the last trimester of pregnancy, following a 200 mg single oral dose of proguanil. Four of these women were restudied 2 months after delivery. The pharmacokinetic properties of proguanil were similar during and after pregnancy. Median peak plasma concentrations of proguanil during pregnancy and following delivery were 212 and 215 ng·ml−1, and occurred at 4.5 and 5 h, respectively. Mean plasma AUC values for proguanil during and following pregnancy were 94 and 98 ng·h·ml−1·kg−1, respectively. Corresponding whole blood AUC values were 361 and 396 ng·h·ml−1·kg−1. The mean elimination half lives and mean residence times of proguanil in plasma and whole blood were 12.3 and 19.6 h and 13.8 and 20.7 h respectively during pregnancy. Following pregnancy these values were 17.1 and 19.7 h for plasma and 19.7 h and 20.2 h for whole blood respectively. Mean peak plasma and whole blood concentrations of cycloguanil following pregnancy were 25 and 22 ng·ml−1 respectively. During pregnancy peak cycloguanil concentrations in both plasma and whole blood were markedly lower, 13 and 12 ng ml−1, respectively. Two pregnant women (neither of whom were restudied) were probably poor metabolisers of proguanil. The mean ratio of proguanil to cycloguanil plasma AUC was 16.7 in the third trimester of pregnancy and 7.8 following pregnancy, compared with less than 5 in previously reported studies. The concentrations of 4-chlorophenylbiguanide in both plasma and whole blood in pregnant subjects were also lower than those after pregnancy. These data show that blood concentrations of the active antimalarial metabolite cycloguanil are reduced in late pregnancy and that the currently recommended dose of proguanil could be inadequate for antimalarial prophylaxis in pregnant women.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 44 (1993), S. 265-269 
    ISSN: 1432-1041
    Keywords: Cyclosporine ; Renal transplantation ; pharmacokinetics ; intraindividual variation ; circadian variation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The intraindividual variability and circadian variation of oral cyclosporine (CsA) pharmacokinetics were studied over 24 h in 18 renal transplant recipients at steady state, and in 10 of the patients during a second 24 h period. The absolute percentage intraindividual difference in daytime AUC (0–12 h) ranged from 2% to 54% (mean 30%), and the corresponding variability in nighttime AUC (0–12 h) ranged from 5% to 80% (mean 34%). The pharmacokinetic variables t1/2, tmax and Cmax were more variable than the AUC (0–12 h) both during the day and at night. The evening trough level was significantly lower than the morning trough level; 185 ng · ml−1 versus 223 ng · ml−1. This, together with a significantly longer t1/2 in the night than the day, suggested circadian variability in the pharmacokinetics of CsA. In a separate retrospective study in 162 renal transplant recipients given CsA by constant intravenous infusion, repeated CsA blood concentration measurements at steady state showed lower concentrations during the day than the night, suggesting higher CsA clearance during daytime. It is concluded that CsA pharmacokinetics in renal transplant recipients, besides the well-known interindividual variability, also displays large intraindividual variability as well as circadian variation. Our findings further emphasize the necessity and difficulty of pharmacological monitoring in the clinical use of CsA in organ transplantation.
    Type of Medium: Electronic Resource
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