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  • Articles  (481)
  • Nitrogen fixation  (258)
  • bioavailability  (223)
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  • Articles  (481)
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  • Springer  (481)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    European journal of nutrition 22 (1983), S. 185-194 
    ISSN: 1436-6215
    Keywords: sugar substitutes ; D-glucose ; bioavailability ; D-glucitol (D-sorbitol) ; D-mannitol ; Palatinit® ; D-glucosyl-α(1→1)-D-mannitol ; D-glucosyl-α(1→6)-D-glucitol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Zusammenfassung Zur Vertiefung des Verständnisses vom Stoffwechsel des Zuckeraustauschstoffes Palatinit® wurden seine zwei Bestandteile D-Glucosyl-α(1→1)-D-mannit und D-Glucosyl-α(1→6)-D-glucit [D-Glucosyl-α(1→6)-D-sorbit] nach dem Verfahren von Karimzadegan et al. auf ihre Glucose-Bioverfügbarkeit an ketotischen Ratten untersucht. Bei Umwandlungsraten in Glucose von 6 bzw. 20 % für Mannit und Glucit (Sorbit) sowie von 39 bzw. 42% für Glucosylmannit und Glucosylglucit erhält demnach der metabolische Glucose-Pool nicht das volle Glucose-Äquivalent aus diesen Verbindungen. Von dem Anteil an präformierter Glucose in den Glucosylhexiten — theoretisches Maximum 50 % — sind nur 36 % aus Glucosylmannit bzw. 32 % aus Glucosylglucit bioverfügbar. Die im Vergleich zur Theorie verminderte Bioverfügbarkeit von Glucose aus Palatinit® wird auf partiellen mikrobiellen Abbau in unteren Darmabschnitten zurückgeführt. Die an Ratten erhaltenen Ergebnisse werden auch für alle anderen Spezies gelten, welche in Caecum und/oder Colon Kohlenhydrate vergären. Die Unterschiede zwischen D-Glucosyl-α(1→1)-D-mannit und D-Glucosyl-α(1→6)-D-glucit werden durch unterschiedliche Verzögerung der Glucoseresorption im Dünndarm, wo auch D-Glucit angreift, bedingt. Die Ermittlung der Glucose-Bioverfügbarkeit gewährt weitgehende Einblicke in das Schicksal von Kohlenhydraten einschließlich der Symbiose zwischen Säugetier und Mikroorganismen im Dickdarm. Da ein ziemlich vollständiger Überblick über die metabolischen Konsequenzen nach ihrer Zufuhr erhalten wird, sollte das Verfahren zur Messung der Bioverfügbarkeit von Glucose daher bei Abschätzungen der Lebensmittelsicherheit anderer Zuckeraustauschstoffe ebenfalls angewandt werden.
    Notes: Summary For the sake of metabolic insight into the fate of the sugar substitute Palatinit®, its two components D-glucosyl-α(1→1)-D-mannitol and D-glucosyl-α(1→6)-D-glucitol [D-glucosyl-α-(1→6)-D-sorbitol] were assayed for glucose bioavailability by the procedure of Karimzadegan et al. using ketotic rats. With conversion rates into glucose of 6 and 20 %, respectively, for free mannitol and glucitol (sorbitol), 39 % for glucosylmannitol and 42 % for glucosylglucitol, the metabolic glucose pool of the rat does not receive the full carbohydrate complement of these compounds. The preformed glucose moiety of the glucosylhexitols is bioavailable by 36 and 32 %, respectively, from glucosylmannitol and glucosylglucitol, with 50 % as theoretical maximum. Less than theoretical bioavailability of glucose from Palatinit® is ascribed to microbial attack in the hindgut. The data on rats are held valid also for other species demonstrating carbohydrate fermentation in the caecum and/or colon. Differences between D-glucosyl-α(1→1)-D-mannitol and D-glucosyl-α(1→6)-D-glucitol are caused by a differential delay of glucose absorption in the small intestine, also exerted by D-glucitol. The deep metabolic insight offered by the glucose bioavailability assay into the fate of carbohydrates includes the mammal-microbial symbiosis in the large bowel. Since a rather complete survey of the metabolic consequences after their intake can be obtained, the assay system should be generally applied in assessments of food safety also of other sugar substitutes.
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  • 2
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    Biology and fertility of soils 4 (1987), S. 61-66 
    ISSN: 1432-0789
    Keywords: Stem nodulation ; Aeschynomene afraspera ; Legume ; Nitrogen fixation ; Acetylene reduction assay (ARA)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Aeschynomene afraspera is a wild annual legume growing in periodically waterlogged soils in western Africa. This legume is characterized by a profuse stem nodulation. Nodules are formed on the stem at the emergence of lateral root primordia, called nodulation sites. These sites are irregularly distributed on vertical rows all along the stem and branches. Stem nodules are hemispherically shaped. Their outside is dark green and they contain a red-pigmented central zone. Stem nodules exhibit a high nitrogen-fixing potential. Acetylene reduction assays result in stem nodule activity of 309 μmol C2H4 g−1 dry nodule h−1. Field-grown stem nodulated Aeschynomene accumulated more N (51 g N m−2 in 10 weeks) than the root nodulated one. Because of this nitrogenfixing potential and its ability to grow in waterlogged conditions, A. afraspera could probably be introduced into tropical rice cropping systems.
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  • 3
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    Biology and fertility of soils 8 (1989), S. 356-368 
    ISSN: 1432-0789
    Keywords: Plant-root associations ; Azospirillum spp ; Rhizosphere ; Nitrogen fixation ; Acetylene reduction assay (ARA) ; Phytohormones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Bacteria of the genus Azospirillum are extensively studied for their plant-growth promoting effect following inoculation. Physiological and biochemical studies of these diazotrophic bacteria are now benefiting from recent breakthroughs in the development of genetic tools for Azospirilum. Moreover, the identification and cloning of Azospirillum genes involved in N2 fixation, plant interaction, and phytohormone production have given new life to many research projects on Azospirillum. The finding that Azospirillum genes can complement specific mutations in other intensively studied rhizosphere bacteria like Rhizobia will certainly trigger the exploration of new areas in rhizosphere biology. Therefore a review of the Azospirillum-plant interactions is particularly timely.
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  • 4
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    Biology and fertility of soils 5 (1987), S. 83-87 
    ISSN: 1432-0789
    Keywords: Inoculation ; Inoculum dose ; Nitrogen fixation ; Chickpea ; Rhizobium spp. ; Cicer arietinum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The influence of three inoculum rates on the performance of three chickpea (Cicer arietinum L.) Rhizobium strains was examined in the field on a Mollisol soil. Increasing amounts of inoculum improved the performance of the strains. A normal dose (104 cells per seed) applied at different intervals gave non-significant increases in nodulation, nitrogenase activity (acetylene reduction assay), nitrogen uptake and grain yield. A ten-fold increase in inoculum increased nodule number, shoot dry weight, nitrogenase activity (ARA) and grain yield, but increases over the control were significant only for nodule dry weight and nitrogen uptake by shoot and grain. The highest level of inoculum (100 × normal) significantly increased nodule dry weight, grain yield, total nitrogenase activity (ARA) and nitrogen uptake by shoot and grain. Strain TAL 620 was more effective than the other two. Combined nitrogen (60 kg N ha−1) suppressed nodulation and nitrogenase activity (ARA).
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  • 5
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    Biology and fertility of soils 6 (1988), S. 39-44 
    ISSN: 1432-0789
    Keywords: Alnus ; Energy forestry ; Frankia ; Meadow soil ; Nitrogen fixation ; Nodulation ; Peat soil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Use of the N2-fixing grey alder, Alnus incana (L.) Moench, as a short-rotation crop for energy production is currently being explored. To evaluate the need for inoculation of alders, the distribution of infective propagules of Frankia in the soil at potential sites for alder plantations was examined. Uninoculated grey alder seedlings were grown in three types of soil. Frequent nodulation was found in a meadow soil which had been free from actinorhizal plants for nearly 60 years, but the alder seedlings failed to nodulate in peat soil from two different bog sites. One of these bogs had been exploited for peat and the surface layer of the peat had been removed, so that the soil samples were taken from deep layers of the peat. At the other site, an area of cultivated peat, there were no infective propagules of Frankia in plots without alders; the infective Frankia was present in plots only where it had been introduced by inoculated alders. There was no detectable air-borne dispersal of Frankia. Instead, water movement might account for the dispersal of Frankia in peat. Although the apparent absence of Frankia in these peat soils necessitates inoculation of alder seedlings before planting out, this makes it possible to introduce and maintain Frankia strains with selected beneficial characteristics, since there is no competition from an indigenous Frankia flora.
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  • 6
    ISSN: 1432-0789
    Keywords: Nodule damage ; Rivellia angulata ; Nitrogen fixation ; Cajanus cajan ; Pigeonpea ; Vertisol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Damage caused by Rivellia angulata larvae to pigeonpea root nodules at the ICRISAT center in India was greater in the crop grown on Vertisols (up to 86%) compared to that on Alfisols (20%). Attempts to quantify the field effects of nodule damage on growth and yield of pigeonpea in a Vertisol, involving many heavy applications of soil insecticides (aldrin and hexachlorocyclohexane) failed because the insecticides did not control the pest and adversely affected the growth of the pigeonpea and the subsequent crop of sorghum (Sorgorum bicolor L. Moench). The impact of nodule damage on pigeonpea growth, yield and nutrient uptake was successfully studied in greenhouse-grown plants at three N levels. In this pot study, artificial inoculation with Rivellia sp. led to substantial nodule damage (70%). The results of this damage were a significant overall reduction in nodule dry weight (46%), acetylene reduction activity (31%), total leaf area (36%), chlorophyll content of leaves (39%) and shoot dry weight (23%) 68 days after sowing. At maturity, Rivellia sp. infestation caused significant reductions in top dry weight (22%), root and nodule dry weight (27%), seed dry weight (14%), and total N (29%) and P uptake (19%). The problems and prospects of manipulating nodule damage so as to reduce N losses in pigeonpea are discussed.
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  • 7
    ISSN: 1432-0789
    Keywords: Triticum aestivum ; T. turgidum ; Nitrogen fixation ; Field inoculation ; Acetylene reduction assay (ARA)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Eight commercial Israeli spring wheat cultivars (six Triticum aestivum and two T. turgidum) grown with 40 and 120 kg N/ha were tested for responses to inoculation with Azospirillum brasilense. At the low level of N fertilization (40 kg/ha), five cultivars showed significant increases in plant dry weight measured at the milky ripe stage; however, by maturation only the cultivar “Miriam” showed a significant increase in grain yield. Two cultivars, which had shown a positive inoculation effect at the earlier stages, had a significant decrease in grain yield. No significant effect of inoculation was found at the high N level. To confirm those results, four wheat (T. aestivum) cultivars were tested separately over 4 years in 4 different locations under varying N levels. Only Miriam showed a consistently positive effect of Azospirillum inoculation on grain yield. Inoculation increased the number of roots per plant on Miriam compared with uninoculated plants. This effect was found at all N levels. Nutrient (N, P and K) accumulation and number of fertile tillers per unit area were also enhanced by Azospirillum, but these parameters were greatly affected by the level of applied N. It is suggested that the positive response of the spring wheat cultivar “Miriam” to Azospirillum inoculation is due to its capacity to escape water stresses at the end of the growth season.
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  • 8
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    Biology and fertility of soils 4 (1987), S. 15-19 
    ISSN: 1432-0789
    Keywords: Nitrogen fixation ; N-balance studies ; Azolla ; Blue-green algae ; Chemical N fertilization ; Rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A nitrogen balance study conducted in ceramic pots under net house conditions for four seasons showed that flooded rice soil leaves a positive nitrogen balance (N increase) in soil after rice cropping in both fertilized and unfertilized soil. Recovery of nitrogen from rice soil was more than its input in unfertilized soil, but it was reverse in fertilized soil. Incorporation of Azolla or BGA twice as basal and 20 days after transplanting (DAT) alone or in combination showed higher nitrogen balance and N2-fixation (N gain) in soil than in that where it was applied once either as basal or 20 DAT. Planted soil showed more N2-fixation than that of fallow rice, and flooded soil fixed more nitrogen in comparison to non-flooded soil in light but less in dark. Soil exposed to light fixed more nitrogen than that of unexposed soil in both flooded and non-flooded conditions.
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  • 9
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    Biology and fertility of soils 4 (1987), S. 9-14 
    ISSN: 1432-0789
    Keywords: Rhizosphere ; Nitrogen fixation ; Root exudates ; Soil bacteria ; Carbon budget ; Rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The association of rice seedlings (cv. Delta) with different strains of Azospirillum was studied under monoxenic conditions in the dark. Axenic 3-day-old seedlings were obtained on a C- and N-free medium and inoculated with 6 · 107 bacteria per plant in a closed vial. Seven days later, different components of a carbon budget were evaluated on them and on sterile controls: respired CO2, carbon of shoot and roots, bacterial and soluble carbon in the medium. Two strains (A. lipoferum 4B and A. brasilense A95) isolated from the rhizosphere of rice caused an increase in exudation, + 36% and + 17% respectively compared with sterile control. Shoot carbon incorporation and respiration were reduced by inoculation. A third strain (A. brasilense R07) caused no significant change in exudation. A. lipoferum B7C isolated from maize did not stimulate rice exudation either. We further investigated a possible effect of nitrogen fixation on this phenomenon: inhibition of nitrogen fixation by 10% C2H2 did not modify the extent of C exudation by rice associated with A. lipoferum 4B or with the non-motile A. lipoferum 4T.
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  • 10
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    Biology and fertility of soils 7 (1989), S. 269-274 
    ISSN: 1432-0789
    Keywords: Nitrogen fixation ; Frankia-Ceanothus spp. association ; Acetylene reduction assay (ARA) ; Microsymbiont population ; Nodules ; Actinomycetes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Wildland shrub improvement is needed for sound range and disturbed land revegetation practice. The possibility of selecting superior N2-fixingFrankia-Ceanothus spp. actinorhizal associations was examined. Greenhouse tests were used to expose various soil-borne microsymbiont andCeanothus sp. population accessions in reciprocal combination. The acetylene reduction rate was used as a measure of N2-fixation capacity. There was no significant interaction between host and microsymbiont regardless of source for all variables measured. The acetylene reduction rate, nodule number and mass, plant biomass, and root: shoot ratio were significantly different among soil sources. The acetylene reduction rate was not significantly different amongCeanothus sp. accessions. Neither was it strongly correlated with other variables. It was concluded that the N2-fixation rate is more a function ofFrankia sp. than the hostCeanothus sp. in actinorhizal associations. It appears possible to select soil sources with superior N2-fixing microsymbiont populations.
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  • 11
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    Biology and fertility of soils 6 (1988), S. 279-281 
    ISSN: 1432-0789
    Keywords: Sesbania rostrata ; Green manure ; Biofertilizer ; Nitrogen fixation ; Stem nodule
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Ratooning and stem cutting were compared with seeding in order to reduce the amount of seeds of Sesbania rostrata for green-manure growth. Both methods increased the biofertilizer yield highly significantly within a 6-week growth period.
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  • 12
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    Journal of molecular evolution 21 (1984), S. 19-32 
    ISSN: 1432-1432
    Keywords: Leghemoglobin ; Gene duplication ; Gene linkage ; Concerted evolution ; Nitrogen fixation ; Soybean
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have analyzed the sequences of soybean leghemoglobin genes as an initial step toward understanding their mode of evolution. Alignment of the sequences of plant globin genes with those of animals reveals that (i) based on the proportion of nucleotide substitutions that have occurred at the first, second, and third codon positions, the time of divergence of plant and animal globin gene families appears to be extremely remote (between 900 million and 1.4 billion years ago, if one assumes constancy of evolutionary rate in both the plant and animal lineages) and (ii) in addition to the normal regulatory sequences on the 5′ end, an approximately 30-base-pair sequence, specific to globin genes, that surrounds the cap site is conserved between the plant and animal globin genes. Comparison of the leghemoglobin sequences with one another shows that (i) the relative amount of sequence divergence in various coding and noncoding regions is roughly similar to that found for animal globin genes and (ii) as in animal globin genes, the positions of insertions and deletions in the intervening sequences often coincide with the locations of direct repeats. Thus, the mode of evolution of the plant globin genes appears to resemble, in many ways, that of their animal counterparts. We contrast the overall intergenic organization of the plant globin genes with that of animal genes, and discuss the possibility of the concerted evolution of the leghemoglobin genes.
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  • 13
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    European journal of nutrition 28 (1989), S. 130-141 
    ISSN: 1436-6215
    Keywords: bioavailability ; folic acid ; pharmaceutical preparation ; Bioverfügbarkeit ; Folsäure ; Arzneimittelzubereitung
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Zusammenfassung Untersuchungen zur Bioverfügbarkeit essentieller Mikronährstoffe (Vitamine, Mineralstoffe, Spurenelemente) aus Lebensmitteln wie auch aus Arzneimittelzubereitungen sind von entscheidender Bedeutung bei der Beurteilung des jeweiligen Beitrages zur Nährstoffversorgung bzw. zur Abschätzung eines möglichen Therapieerfolges. Die Durchführung derartiger Prüfungen erfolgt in der Praxis nicht selten nach unterschiedlichen Kriterien. Deshalb werden zunächst die Grundsätze erläutert, die bei entsprechenden Prüfungen für eine valide Bewertung von Nähr- bzw. Wirkstoffgemischen oder Monopräparaten bedeutsam sind. Abschließend wird die Ermittlung der Bioverfügbarkeit von Folsäure an einem Beispiel demonstriert. Zur Testung werden die postresorptiven Kurvenintegrale ermittelt, wobei die Daten auf das basale Ausgangsniveau bezogen werden. Zur Beurteilung der Bioverfügbarkeit findet neben dem maximalen Vitaminanstieg im Serum sowie der Zeit bis zum Konzentrationsmaximum insbesondere der Bioverfügbarkeitsquotient von Test- und Referenzzubereitung mit seinem 95%-VB Berücksichtigung. Die Ergebnisse zeigen, daß die exemplarisch eingesetzte Testsubstanz, 5-Formyl-Tetrahydrofolsäure, eine sehr gute Bioverfügbarkeit aufweist und daß unter Anwendung der beschriebenen Rahmenbedingungen eine objektive Bewertung der Bioverfügbarkeit möglich ist.
    Notes: Summary Bioavailability studies of micronutrients (vitamins, minerals) from different food stuffs, as well as from pharmaceutical preparations are of great importance for the calculation of nutrient intake and/or the evaluation of the therapeutic value. In practice, bioavailability studies are not generally performed on a standardized level. For this reason basic criterions are presented and discussed. Finally, the investigation of the bioavailability of folate is demonstrated by an example. The parameters investigated are: the maximal concentration (cmax), the time to reach this maximum (tmax), and especially the bioavailability ratio determined from the area under the curve (AUC) after administration of the folic acid containing test and reference preparation. The results indicate that 5-formyl-tetrahydrofolic acid given in the tested form has nearly the same bioavailability (ratio: 1.02) as folic acid (pteroylmonoglutamic acid) in aqueous solution.
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  • 14
    ISSN: 1432-2048
    Keywords: Alnus ; Ammonium ; Carbon translocation ; Endophyte damage ; Nitrogen fixation ; Root nodule
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cloned plants of Alnus incana (L.) Moench were inoculated and grown without combined nitrogen for seven weeks. The effects of ammonium on the function and structure of the root nodules were studied by adding 20 mM NH4Cl (20 mM KCl=control) for four days. Nitrogenase activity decreased to ca. 50% after one day and to less than 10% after two days in ammonium treated plants, but was unaffected in control plants. The results were similar at photon flux densities of 200 and 50 μmol m-2 s-1. At the higher light level the effect was concentration dependent between 2 and 20 mM NH4Cl. The recovery was slow, and more than 11 d were needed for plants treated with 20 mM ammonium to reach initial activity. The distribution of 14C to the root nodules after assimilation of 14CO2 by the plants was not changed by the ammonium treatment. Microscopical studies of root nodules showed high frequencies of endophyte vesicles being visually damaged in nodules from ammonium-treated plants, but not in nodules from control plants. When nitrogenase activity was restored, visually damaged vesicles were again few, whereas young developing vesicles were numerous. The slow recovery, the 14C-translocation pattern, and the structural changes of the endophyte indicate a more complex mechanism of ammonium influence than simply a short-term reduction in supply of carbon compounds to the nodules.
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  • 15
    ISSN: 1432-2048
    Keywords: Ammonia ; Nitrogen fixation ; Nodule ; Senescence (root nodules) ; Ureide ; Vigna
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract During early development (up to 18 d after sowing) of nodules of an “effective” cowpea symbiosis (Vigna unguiculata (L.) Walp cv. Vita 3: Rhizobium strain CB756), rapidly increasing nitrogenase (EC 1.7.99.2) activity and leghaemoglobin content were accompanied by rapid increases in activities of glutamine synthetase (EC 6.3.1.2), glutamate synthase (EC 2.6.1.53), enzymes of denovo purine synthesis (forming inosine monophosphate) xanthine oxidoreductase (EC 1.2.3.2), urate oxidase (EC 1.7.3.3), phosphoenolpyruvate carboxylase (EC 4.1.1.31) and led to increased export of ureides (allantoin and allantoic acid) to the shoot of the host plant in the xylem. Culturing plants with the nodulated root systems maintained in the absence of N2 (in 80 Ar: 20 O2, v/v) had little effect on the rates of induction and increase in nitrogenase activity and leghaemoglobin content but, in the absence of N2 fixation and consequent ammonia production by bacteroids, there was no stimulation of activity of enzymes of ammonia assimilation or of the synthesis of purines or ureides. Addition of NO 3 - (0.1–0.2 mM) relieved host-plant nitrogen deficiency caused by the Ar: O2 treatment but failed to increase levels of enzymes of N metabolism in either the bacteroid or the plant-cell fractions of the nodule. Premature senescence in Ar: O2-grown nodules occurred at 18–20 d after sowing, and resulted in reduced levels of nitrogenase activity and leghaemoglobin but increased the activity of hydroxybutyrate oxidoreductase (EC 1.1.1.30).
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  • 16
    ISSN: 1432-2048
    Keywords: Auxin (IAA), production by Rhizobium ; Gibberellin production by Rhizobium ; Mutant (Rhizobium) ; Nitrogen fixation ; Phaseolus (nodulation) ; Rhizobium (mutants) ; Root nodule
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Similar ranges of gibberellins (GAs) were detected by high-performance liquid chromatography (HPLC)-immunoassay procedures in ten cultures of wild-type and mutant strains of Rhizobium phaseoli. The major GAs excreted into the culture medium were GA1 and GA4. These identifications were confirmed by combined gas chromatographymass spectrometry. The HPLC-immunoassays also detected smaller amounts of GA9- as well as GA20-like compounds, the latter being present in some but not all cultures. In addition to GAs, all strains excreted indole-3-acetic acid (IAA) but there was no obvious relationship between the amounts of GA and IAA that accumulated. The Rhizobium strains studied included nod − and fix − mutants, making it unlikely that the IAA- and GA-biosynthesis genes are closely linked to the genes for nodulation and nitrogen fixation. The HPLC-immunoassay analyses showed also that nodules and non-nodulated roots of Phaseolus vulgaris L. contained similar spectra of GAs to R. phaseoli culture media. The GA pools in roots and nodules were of similar size, indicating that Rhizobium does not make a major contribution to the GA content of the infected tissue.
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  • 17
    ISSN: 1432-2048
    Keywords: Ammonium assimilation ; Glycine ; Nitrogen fixation ; Proplastid ; Purine synthesis ; Root nodule ; Ureide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Subcellular organelle fractionation of nitrogen-fixing nodules of soybean (Glycine max (L.) Merr.) indicates that a number of enzymes involved in the assimilation of ammonia into amino acids and purines are located in the proplastids. These include asparagine synthetase (EC 6.3.1.1), phosphoribosyl amidotransferase (EC 2.4.2.14), phosphoglycerate dehydrogenase (EC 1.1.1.95), serine hydroxymethylase (EC 2.1.2.1), and methylene-tetrahydrofolate dehydrogenase (EC 1.5.1.5). Of the two isoenzymes of asparate aminotransferase (EC 2.6.1.1) in the nodule, only one was located in the proplastid fraction. Both glutamate synthase (EC 1.4.1.14) and triosephosphate isomerase (EC 5.3.1.1) were associated at least in part with the proplastids. Glutamine synthetase (EC 6.3.1.2) and xanthine dehydrogenase (EC 1.2.1.37) were found in significant quantities only in the soluble fraction. Phosphoribosylpyrophosphate synthetase (EC 2.7.6.1) was found mostly in the soluble fraction, although small amounts of it were detected in other organelle fractions. These results together with recent organelle fractionation and electron microscopic studies form the basis for a model of the subcellular distribution of ammonium assimilation, amide synthesis and uredie biogenesis in the nodule.
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  • 18
    ISSN: 1432-2048
    Keywords: Carbon dioxide fixation ; Citrulline ; Coralloid roots ; Cycads (nitrogen fixation) ; Nitrogen fixation ; Nitrogen transport ; Nostoc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Freshly detached coralloid roots of several cycad species were found to bleed spontaneously from xylem, permitting identification of products of nitrogen transfer from symbiotic organ to host. Structural features relevant to the export of fixed N were described for Macrozamia riedlei (Fisch. ex Gaud.) Gardn. the principal species studied. Citrulline (Cit), glutamine (Gln) and glutamic acid (Glu), the latter usually in a lesser amount, were the principal translocated solutes in Macrozamia (5 spp.), Encephalartos (4 spp.) and Lepidozamia (1 sp.), while Gln and a smaller amount of Glu, but no Cit were present in xylem sap of Bowenia (1 sp.),and Cycas (2 spp.). Time-course studies of 15N enrichment of the different tissue zones and the xylem sap of 15N2-pulse-fed coralloid roots of M. riedlei showed earlier 15N incorporation into Gln than into Cit, and a subsequent net decline in the 15N of Gln of the coralloid-root tissues, whereas Cit labeling continued to increase in inner cortex and stele and in the xylem sap. Hydrolysis of the 15N-labeled Cit and Gln consistently demonstrated much more intense labeling of the respective carbamyl and amide groups than of the other N-atoms. Coralloid roots of M. riedlei pulse-fed 14CO2 in darkness showed 14C labeling of aspartic acid (Asp) and Cit in all tissue zones and of Cit of xylem bleeding sap. Lateral roots and uninfected apogeotropic roots of M. riedlei and M. moorei also incorporated 14CO2 into Cit. The 14C of Cit was restricted to the carbamyl-C. Comparable 15N2 and CO2-feeding studies on corallid roots of Cycas revoluta showed Gln to be the dominant product of N2 fixation, with Asp and alanine as other major 14C-labeled amino compounds, but a total absence of Cit in labeled or unlabeled form.
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  • 19
    ISSN: 1432-2048
    Keywords: Allantoin ; Amino acids ; Bleeding sap ; Nitrogen fixation ; Phaseolus
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    Topics: Biology
    Notes: Abstract Dwarf french beans, Phaseolus vulgaris L., were grown with or without inoculation with rhizobia (strain 3644), and with or without a combined nitrogen source (nitrate or ammonium ions). The distribution of radioactivity into products of dark 14CO2 assimilation was studied in roots or nodules from these plants. A detailed study was also made of the distribution and rates of excretion of nitrogen in xylem bleeding sap in 28 day old plants grown on the various sources of nitrogen. Whereas detached nodules accumulated radioactive glycine, serine and glutamate when incubated with 14CO2, bleeding sap from plants root fed 14CO2 contained low levels of radioactivity in these compounds but higher levels in allantoin. Chemical analysis showed allantoin to be the major compound transported in the xylem of nodulated plants, whether or not they were fed on combined nitrogen. In contrast uninoculated plants accumulated mainly amino acids in the bleeding sap, the amount and chemical composition of which depended on the combined nitrogen source.
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  • 20
    ISSN: 1432-2048
    Keywords: Glyoxylate ; Isonicotinic acid hydracide ; Medicago ; Nitrogen fixation ; Photorespiration ; Rhizobium
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    Topics: Biology
    Notes: Abstract Nitrogen fixation (measured as acetylene reduction) by whole nodulated alfalfa plants was stimulated when the plants were treated with isonicotinic acid hydracide (INH) and glyoxylate, both inhibitors of the glycolate pathway of carbohydrate metabolism, at concentrations of 300 and 100 mM, respectively. Reducing energetic loses caused by photorespiration results in an increase in the symbiotic nitrogen fixation.
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  • 21
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    Planta 152 (1981), S. 544-552 
    ISSN: 1432-2048
    Keywords: Ammonium assimilation ; Lichens ; Nitrogen fixation ; Peltigera
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    Topics: Biology
    Notes: Abstract The Nostoc in the cephalodia of the lichen Peltigera aphthosa Willd. fixed 15N2 and the bulk of the nitrogen fixed was continuously transferred from it to its eukaryotic partners (a fungus and a green alga, Coccomyxa sp.). Kinetic studies carried out over the first 30 min, after exposure of isolated cephalodia to 15N2, showed that highest initial 15N2-labelling was into NH 4 + . After 12 min little further increase in the NH 4 + label occurred while that in the amide group of glutamine and in glutamate continued to increase. The 15N-labelling of the amino group of glutamine and of aspartate increased more slowly, followed by an increase in the labelling of alanine. When total incorporation of 15N-label was calculated, the overall pattern was found to be rather similar except that, throughout the experiment, the total 15N incorporated into glutamate was about six times greater than that into the amide group of glutamine. Pulse chase experiments, in which 14N2 was added to cephalodia previously exposed to 15N2, showed that the NH 4 + pool rapidly became depleted of 15N-label, followed by decreases in the labelling of glutamate, the amide group of glutamine and aspartate. The 15N-labelling of alanine, however, continued to increase for a period. When isolated cephalodia were treated with L-methionine-SR-sulphoximine, an inhibitor of glutamine synthetase (EC 6.3.1.2), and azaserine, an inhibitor of glutamate synthase (EC 2.6.1.53), there was no detectable labelling in glutamine although the 15N-labelling of glutamate increased unimpaired. On treating the cephalodia with amino-oxyacetate, an inhibitor of aminotransferase activity, the alanine pool decreased. Evidence was obtained that glutamine synthetase and glutamate synthase were located in the Nostoc, and that glutamate dehydrogenase (EC 1.4.1.4) and various amino-transferases were located in the cephalodial fungus. Possible implications of these findings are discussed.
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  • 22
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    Oecologia 79 (1989), S. 566-568 
    ISSN: 1432-1939
    Keywords: Carbon dioxide ; Lichen ; Lobaria ; Nitrogen fixation
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    Topics: Biology
    Notes: Summary Thalli of Lobaria pulmonaria (L.) Hoffm., a nitrogen-fixing epiphyte common in mesic temperate forests, were collected in a Douglas-fir (Pseudotsuga menziesii Franco) forest near Corvallis, Oregon, and maintained for 20 to 40 days in controlled-environment chambers with atmospheric CO2 concentrations of 374 and 700 μll-1. Nitrogenase activity, which was assayed by the acetylene reduction method, was approximately doubled in the lichen maintained in elevated CO2. Increases in nitrogen fixation by lichens may be an important part of the integrated ecosystem response to rising CO2.
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  • 23
    ISSN: 1432-1939
    Keywords: Lupinus succulentus ; Fabaceae ; Lupine ; Quinolizidine alkaloids ; Nitrogen fixation ; Defoliation ; Plant-herbivore interactions
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    Topics: Biology
    Notes: Summary We examined the effects of nitrogen nutrition and defoliation on the alkaloids, nitrogen levels, and growth of Lupinus succulentus by growing plants under five nitrogen/defoliation treatments: 1) fertilization with a high-nitrate nutrient solution, 2) fertilization with a low-nitrate solution, 3) inoculation with N-fixing bacteria but without available soil nitrogen, 4) high-nitrate solution plus periodic partial defoliation, and 5) low-nitrate plus defoliation. In the absence of defoliation, plants from both the N-fixing and high-N treatments had higher concentrations of alkaloids and nitrogen, and higher growth rates than the low-N plants. Periodic defoliation had little effect on the high-N plants, but defoliated N-fixing plants were severely stunted and had lower alkaloid and nitrogen levels. The experimental treatments also affected the relative concentrations of the alkaloids. Our results indicate that 1) alkaloid composition and concentration in L. succulentus are determined by both nitrogen availability and developmental state, 2) plants relying solely on N-fixation respond quite differently to defoliation than those with adequate soil nitrogen, and 3) the food value of the plant tissue can be affected by an interaction between the effects of defoliation and nitrogen status.
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  • 24
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    European journal of clinical pharmacology 32 (1987), S. 631-634 
    ISSN: 1432-1041
    Keywords: salbutamol ; albuterol ; pharmacokinetics ; bioavailability ; healthy volunteers
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Salbutamol was administered to sixteen healthy male volunteers intravenously and by mouth in liquid, tablet, and capsule form using a Latin-Squares design. Pharmacokinetic parameters from intravenous data were similar to previously reported values obtained with oral administration, with a mean terminal half-life of 3.8 h and a mean clearance of 439 ml·min−1·1.73 m−2. Peak plasma concentrations of 10–20 ng·ml−1 were obtained 1–3 h following oral administration. The absolute bioavailability of each of the oral preparations was 44%. While statistically significant differences in lag time and time to peak concentration were noted among the various oral preparations, the drug is rapidly absorbed in all three dosage forms and the observed differences are unlikely to be of clinical significance.
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  • 25
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    European journal of clinical pharmacology 34 (1988), S. 77-82 
    ISSN: 1432-1041
    Keywords: N-acetylcysteine ; pharmacokinetics ; bioavailability
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics and bioavailability of N-acetylcysteine (NAC) have been determined after its intravenous and oral administration to 6 healthy volunteers. According to a randomized cross-over design each subject received NAC 200 mg i.v. and 400 mg p.o., and blood samples were collected for 30 h. Reduced NAC had a volume of distribution (VSS) of 0.59 l·kg−1 and a plasma clearance of 0.84 l·h−1·kg−1. The terminal half-life after intravenous administration was 1.95 h. The oral bioavailability was 4.0%. Based on total NAC concentration, its volume of distribution (VSS) was 0.47 l·kg−1 and its plasma clearance was 0.11 l·h−1·kg−1. The terminal half-life was 5.58 h after intravenous administration and 6.25 h after oral administration. Oral bioavailability of total NAC was 9.1%.
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  • 26
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    European journal of clinical pharmacology 34 (1988), S. 315-317 
    ISSN: 1432-1041
    Keywords: albendazole ; echinococcosis ; bioavailability ; food intake ; fatty meal
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary We have studied the systemic availability of oral albendazole in 6 patients with echinococcosis either fasting or with breakfast. Albendazole sulphoxide, the pharmacologically active principle, was assayed by HPLC. Mean plasma concentrations and AUCs were 4.5 times higher when albendazole was given with breakfast than when administered in the fasting state. We conclude that therapy of echinococcosis with albendazole requires the drug to be taken with meals and that administration on an empty stomach might be more appropriate when intraluminal effects are desired, e.g. for intestinal parasites.
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  • 27
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    European journal of clinical pharmacology 34 (1988), S. 469-473 
    ISSN: 1432-1041
    Keywords: xamoterol ; cardiac failure ; beta1-adrenoceptor partial agonist ; pharmacokinetics ; bioavailability
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of xamoterol, a β-adrenoceptor partial agonist under clinical evaluation for the treatment of mild to moderate heart failure, have been studied in 12 healthy male subjects. They received 14 mg i.v. and oral doses of 50 and 200 mg as a tablet and 200 mg as a solution in a 4 way cross-over design. After i.v. dosing the elimination half-life was 7.7 h, the total body clearance was 224 ml·min−1 and the volume of distribution at steady-state (Vss) was 48 l. Sixty-two percent of the dose was recovered unchanged in urine. After oral doses, the absolute bioavailability of xamoterol was shown to be 5% irrespective of whether the dose was administered as a tablet or solution. Peak plasma concentrations occurred at about 2 h for the tablet dose and slightly earlier (1.4 h) for the solution. Peak plasma concentration, AUC and urinary recovery of unchanged drug increased in proportion to dose. The apparent elimination half-life after oral doses (16 h) was significantly longer than that observed after an intravenous dose. Despite the low bioavailability, the degree of inter-subject variability of oral bioavailability was small probably indicating that the controlling factor is the hydrophilic nature of the molecule rather than extensive first pass metabolism or poor dissolution of xamoterol from the tablet formulation.
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  • 28
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    European journal of clinical pharmacology 32 (1987), S. 625-629 
    ISSN: 1432-1041
    Keywords: disopyramide ; bioavailability ; saturable binding ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of disopyramide were determined in 10 healthy volunteers after a 300 mg oral dose and again after a 2mg/kg i.v. dose. The unbound clearance was 599 ml/min and the unbound renal clearance 310 ml/min. The terminal elimination rate constant of unbound drug was 0.180 h−1 after the i.v. dose and 0.203 h−1 after the oral dose. The absorption rate constant was 0.53−1 and the maximum peak concentration occurred after 3.2 h. The bioavailability was 0.809 using the area under the unbound plasma concentration time curve. Although a saturable plasma protein binding was found in all subjects the bioavailability using the total concentration, in contrast to theoretical expectations, showed the same value (0.813) as the unbound concentrations.
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  • 29
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    European journal of clinical pharmacology 34 (1988), S. 211-212 
    ISSN: 1432-1041
    Keywords: diclofenac ; sulglicotide ; bioavailability ; drug interaction
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The bioavailability of diclofenac (D) was assessed in 12 healthy volunteers treated orally with single doses of 100 mg (retard formulation) and subsequently retreated with the same dose of (D) plus sulglicotide (S) 200 mg. (D) blood levels were measured by GLC in samples collected after 1, 2, 4, 6, 8, 12, 24 h. No relevant difference was seen in (D) bioavailability after (S) administration; after 8 h plasma levels of (D) were slightly higher after (S) (p〈0.05), but this difference can be considered incidental only. Thus, sulglicotide does not interfere with the bioavailability of diclofenac, and can be administered concurrently with the latter to prevent possible gastric injury by the antiinflammatory drug.
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  • 30
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    European journal of clinical pharmacology 35 (1988), S. 21-24 
    ISSN: 1432-1041
    Keywords: doxazosin ; hypertension ; alpha-adrenergic blockade ; bioavailability ; pharmacokinetics ; adverse effects
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The antihypertensive effects and steady-state pharmacokinetics of doxazosin, as well as the bioequivalence of four dosage forms, were studied in 25 hypertensive patients. For an 8 mg daily dose mean Cmax at steady-state for all patients was 108 ng/ml; the mean tmax was 1.8 h. The mean terminal elimination half-life was 22 h. The four tablets containing 1, 2, 4, or 8 mg of doxazosin were bioequivalent in delivering the 8 mg dose. In patients with mild to moderate hypertension, 26-day treatment with doxazosin resulted in blood pressure reduction of 10/7 mm Hg in the supine and 13/18 mm Hg in the standing position. Adverse effects were generally mild and of brief duration.
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  • 31
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    European journal of clinical pharmacology 35 (1988), S. 69-75 
    ISSN: 1432-1041
    Keywords: L-carnitine ; pharmacokinetics ; intravenous and oral doses ; bioavailability ; healthy volunteers
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of single intravenous and oral doses of L-carnitine 2 and 6 g was studied in 6 healthy subjects on a low-carnitine diet. Carnitine was more rapidly eliminated from plasma after the 6 g dose. Comparing the doses, the t1/2β of the elimination phase (β) was 6.5 h vs 3.9 h, the elimination constant 0.40 vs 0.50 h−1 and the plasma carnitine clearance was 5.4 vs 6.11 · h−1 for the 2 g and 6 g doses, respectively, showing dose-related elimination. Saturable kinetics were not found. The apparent volumes of distribution after the two doses were not significantly different and were of the same order as the total body water. Urinary recoveries of the 2 g and 6 g doses were 70% and 82%, respectively, during the first 24 h. Following the oral doses, there was no significant difference between the areas under the plasma carnitine concentration-time curves. Urinary recovery was 8% and 4% for the 2 g and 6 g doses during the first 24 h. Oral bioavailability was 16% for the 2 g dose and 5% for the 6 g dose. The results suggest that the mucosal absorption of carnitine was already saturated by the 2 g dose.
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  • 32
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    European journal of clinical pharmacology 35 (1988), S. 89-91 
    ISSN: 1432-1041
    Keywords: flecainide acetate ; Wolff-Parkinson-White syndrome ; rectal absorption ; suppository ; micro enema ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The rectal absorption of flecainide from an aqueous solution, a fatty suppository and a polyethyleneglycol suppository was studied in one patient with supraventricular tachycardia (Wolff-Parkinson-White syndrome) refractory for oral anti-arrhythmic treatment. Rectal absorption was found to be fast (t1/2abs=1 h) and complete when flecainide was administered as a solution (relative bioavailability 100%). Flecainide was poorly absorbed from a fatty suppository. The polyethyleneglycol suppository gave absorption with a relative bioavailability of 80% and t1/2 abs=1.2 h.
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  • 33
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    European journal of clinical pharmacology 35 (1988), S. 183-185 
    ISSN: 1432-1041
    Keywords: xamoterol ; cardiac failure ; beta1-adrenoceptor partial agonist ; pharmacokinetics ; bioavailability
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of xamoterol, a β-adrenergic partial agonist under clinical evaluation for the treatment of mild to moderate heart failure, have been studied in 8 cardiac failure patients (NYHA Class II) of mean age 62 years. After i.v. dosing, the elimination half-life was 7.4±0.4 h, the total body clearance was 228±30 ml·min−1 and the volume of distribution at steady-state was 56±91. 72.5±4.3% of the dose was recovered unchanged in urine. After the oral dose, the absolute bioavailability of xamoterol was shown to be 5.9%. Peak plasma concentrations occurred 1 to 2.5 h after the oral dose. The apparent elimination half-life was significantly longer after oral doses (16±2 h) compared to that observed after an intravenous dose. Renal clearance of xamoterol exceeded glomerular filtration rate as measured by creatinine clearance. The pharmacokinetics of xamoterol in cardiac failure patients with good renal function (creatinine clearance 〉90 ml·min−1) were similar to published data in young healthy male volunteers.
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  • 34
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    European journal of clinical pharmacology 35 (1988), S. 423-425 
    ISSN: 1432-1041
    Keywords: ketorolac tromethamine ; non-narcotic analgesic ; pharmacokinetics ; bioavailability
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of ketorolac tromethamine, a potent non-narcotic analgesic agent used for relief of moderate to severe pain, has been studied in 15 healthy volunteers who received single 10 mg doses intravenously (i.v.), intramuscularly (i.m.) and orally (p.o.) in a three-way cross-over design. The kinetics of i.v. ketorolac were characterized by a terminal half-life of 5.09 h, a small plasma clearance (CL = 0.35 ml·min−1·kg−1) and a small tissue distribution (Vss=0.111·kg−1, Vβ=0.17 l·kg−1; mean (SD). Following i.m. and p.o. administration, peak levels of approximately 0.8 µg/ml were rapidly attained (tmax = 0.8 and 0.9 h, respectively) and the systemic bioavailability was essentially complete.
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  • 35
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    European journal of clinical pharmacology 35 (1988), S. 555-562 
    ISSN: 1432-1041
    Keywords: L-carnitine ; pharmacokinetics ; intravenous — oral doses ; bioavailability
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of single intravenous and oral doses of L-carnitine 2 g and 6 g has been investigated in 6 healthy subjects on a low carnitine diet. Carnitine was more rapidly eliminated from plasma after the higher dose. Comparing the 2-g and 6-g doses, the t1/2β of the elimination phase (β) was 6.5 h vs 3.9 h, the elimination constant was 0.40 vs 0.50 h−1 and the plasma carnitine clearance was 5.4 vs 6.11 × h−1 (p〈0.025), thus showing dose-related elimination. Saturable kinetics was not found in the range of doses given. The apparent volumes of distribution after the two doses were not significantly different and they were of the same order as the total body water. Urinary recoveries after the 2-g and 6-g doses were 70% and 82% during the first 24 h, respectively. Following the two oral dosing, there was no significant difference in AUCs of plasma carnitine. Urinary recoveries were 8% and 4% for the 2-g and 6-g doses during the first 24 h. The oral bioavailability of the 2-g dose was 16% and of the 6 h dose 5%. The results suggest that the mucosal absorption of carnitine is already saturated at the 2-g dose.
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  • 36
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    European journal of clinical pharmacology 35 (1988), S. 385-389 
    ISSN: 1432-1041
    Keywords: oxazepam ; pharmacokinetics ; i.v.-/oral administration ; bioavailability ; healthy volunteers
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Six healthy volunteers received oxazepam 15 mg i.v. and orally at an interval of at least one week. The kinetic variables of i.v. oxazepam were: elimination half-life (t1/2β) 6.7 h, total clearance (CL) 1.07 ml·min−1·kg−1, volume of distribution (Vc) 0.27 l·kg−1 (0.21–0.49) and volume of distribution at steady-state (Vss) 0.59 l·kg−1. The intravenous disposition of unbound oxazepam was characterized by a clearance of 22.5ml·min−1·kg−1 and a distribution volume of 12.3 l·kg−1. After oral oxazepam the peak plasma level was reached in 1.7 to 2.8 h. The plasma t1/2β at 5.8 h was not significantly different from the i.v. value. Absorption was almost complete, with a bioavailability of 92.8%. Urinary recovery was 80.0 and 71.4% of the dose after intravenous and oral administration, respectively. Renal clearance (CLR) of the glucuronide metabolite was 1.10 ml·min−1·kg−1 (0.98–1.52). Oxazepam was extensively bound to plasma protein with a free fraction of 4.5%.
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  • 37
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    European journal of clinical pharmacology 33 (1988), S. 643-645 
    ISSN: 1432-1041
    Keywords: ketoprofen ; food ; bioavailability
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary We have studied the pharmacokinetics of ketoprofen, a non-steroidal anti-inflammatory drug, in 12 patients after a single 100 mg oral dose both in fasting conditions and with a meal. Food significantly affected the peak plasma concentration of ketoprofen and decreased its absorption rate. However, the extent of absorption of ketoprofen, as reflected by the area under the plasma concentration time curve, appeared to be unchanged in the presence of food.
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  • 38
    ISSN: 1432-1041
    Keywords: cyclosporin ; pharmacokinetics ; infusions ; binding ; lipids ; bioavailability
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary On the basis that unbound concentration better correlates with response than total plasma or blood concentration, the inter- and intra-subject variability in the distribution of cyclosporin within blood and to plasma components was studied in renal transplant patients. Pharmacokinetic aspects were also studied. Blood samples were analysed from patients who received the drug both by a 72-h i.v. infusion and orally (7 mg·kg−1 twice daily). Steady-state was reached within 18 h of starting the i.v. infusion; the plasma data were best fitted by a biexponential equation with half-times of 0.13–1.02 h and 4.3–13.9 h, associated with the two phases. The mean plasma clearance was 700 ml/min. Concentrations during the infusions measured by RIA and HPLC were comparable. Oral profiles showed rapid and extensive absorption. The peak plasma concentrations were 1460–1880 µg·l−1 and occurred 2–4 h after dosing, with bioavailability estimates of 41–113%. Concentrations measured by RIA were higher than by HPLC. Blood-to-plasma concentration ratio measurements of cyclosporin at 37°C decreased with increasing plasma concentration and increased with haematocrit. Fraction unbound, measured by ultracentrifugation, was in the range 0.042–0.122 with an average of 0.068, and varied little in some patients but showed systematic changes with time in others. Cyclosporin binding was found to be related not only to the triglyceride but, more particularly, to the cholesterol-related lipoproteins in plasma. Monitoring cholesterol may be helpful in identifying patients with extremes in binding or with widely varying binding.
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  • 39
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    European journal of clinical pharmacology 29 (1986), S. 725-727 
    ISSN: 1432-1041
    Keywords: furosemide ; meal effect ; bioavailability
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary 10 healthy volunteers were given 40 mg furosemide p. o. with and without breakfast. The meal reduced the peak level of furosemide and decreased its bioavailability by approximately 30%. A heavy meal given to 5 of the subjects had no further effect. The reduced bioavailability caused a reduction in the diuretic effect.
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  • 40
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    European journal of clinical pharmacology 37 (1989), S. 409-410 
    ISSN: 1432-1041
    Keywords: cimetidine ; metoclopramide ; antacids ; absorption ; bioavailability ; drug interaction
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Plasma cimetidine levels were determined in 9 normal subjects after a single oral dose of cimetidine 400 mg under control conditions, 2 h before metoclopramide 20 mg and 2 h after a potent antacid. The bioavailability of cimetidine was not significantly affected by metoclopramide and it was marginally reduced by the antacid.
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  • 41
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    European journal of clinical pharmacology 37 (1989), S. 419-421 
    ISSN: 1432-1041
    Keywords: N-Acetylcysteine ; oral administration ; bioavailability ; healthy subjects ; suckable formulation
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics and bioavailability of suckable tablets and granules of N-acetylcysteine (NAC) have been compared after oral administration of 400 mg doses to 10 healthy volunteers. The oral bioavailability of the NAC tablets was 103%. In a multiple dosing study of the same tablets in the same subjects, a high maintenance plasma level of NAC was revealed.
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  • 42
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    European journal of clinical pharmacology 37 (1989), S. 423-426 
    ISSN: 1432-1041
    Keywords: prednisolone ; food intake ; enteric-coated tablets ; pharmacokinetics ; bioavailability
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Prednisolone absorption and bioavailability of 10 mg enteric-coated (EC) and plain (uncoated) tablets were investigated after fasting and heavy meals (EC only) consumed to satiety in normal healthy volunteers. The same volunteers had also received 16 mg of prednisolone intravenously. In fasted subjects, the absolute bioavailability fraction, as normalised for intravenous doses, of prednisolone from plain tablets was 1.055 and from EC tablets was 0.996. The peak concentrations after plain and EC tablets were 309 and 249 ng/ml attained at 0.98 and 5.14 h, respectively. The means plasma elimination half-lives following the plain, EC tablets and intravenous administration in fasting conditions were 3.73, 3.89 and 3.78 h, respectively. Food interfered with both the absorption and the pharmacokinetics of prednisolone after EC tablets resulting in variability in its plasma levels. In some cases absorption of prednisolone was delayed for 12 h and remained at a measurable level for 24 h. In other cases, a normal absorption pattern was observed. This inter- and intrasubject variability of the effect of food appears to be related to its quantity, constituents and also the subjects physiological characteristics. It is concluded that enteric-coated prednisolone tablets should be administered at least 2 h between meals. However, for more predictable corticosteroid absorption (perhaps thus avoiding the therapeutic failure), plain prednisolone tablets are preferable.
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  • 43
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    European journal of clinical pharmacology 17 (1980), S. 111-116 
    ISSN: 1432-1041
    Keywords: zimelidine ; norzimelidine ; antidepressants ; pharmacokinetics ; bioavailability
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The systemic availability of a new antidepressant, zimelidine, and of its pharmacologically active metabolite, norzimelidine, was studied in six healthy male volunteers. Three single doses of zimelidine (25 mg and 100 mg orally and 25 mg i.v.) and two single doses of norzimelidine (25 mg orally and i. v.) were given to each volunteer allowing at least seven days between administrations. Plasma concentrations of zimelidine and norzimelidine were determined in serial blood samples by HPLC. Following oral zimelidine peak plasma concentrations of the metabolite were attained about 3 h after dosing. Oral administration of norzimelidine itself resulted in a plasma concentration profile for this compound that was similar to that observed after oral zimelidine. Utilising the plasma concentration data following intravenous infusion of each compound, the elimination half-lives for zimelidine and norzimelidine were calculated to be 5.1 h (range 4.3–6.0) and 15.5 h (range 10.6–22.9) respectively. The total body clearances of the 2 compounds were similar at 0.52 l · min−1 (range 0.26–0.70) for zimelidine and 0.56 l · min−1 (range 0.28–0.83) for norzimelidine. The substantially longer elimination half-life of norzimelidine was apparently the result of a larger volume of distribution (9.4 l · kg−1; range 7.8–11.4) for this metabolite, as compared to zimelidine (3.21 · kg−1; range 1.6–4.9). The calculated bioavailability of zimelidine was 26% (range 9.1–39) after the 25 mg oral dose, and 29% (range 14–46) after the 100 mg dose. The bioavailability of norzimelidine was 66% (range 36–91). However, oral administration of zimelidine resulted in as much or more norzimelidine reaching the systemic circulation, as the oral administration of norzimelidine itself. This is important as a large part of the activity of the drug may be due to the metabolite.
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  • 44
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    European journal of clinical pharmacology 19 (1981), S. 251-258 
    ISSN: 1432-1041
    Keywords: medigoxin ; digoxin ; dissolution rate ; proportionality ; bioavailability ; prediction
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary We compared our ability to predict the dose of medigoxin and of digoxin required to achieve a fixed serum concentration (the dose requirement) in 33 outpatients. Preliminary work supported the assumptions that the steady state glycoside concentration achieved was proportional to the daily dose given to an individual, and that the bioavailability of the different tablet presentations was similar for either glycoside. We were not able to predict the dose requirement from patient characteristics with any more certainty for medigoxin than for digoxin. Not only the between-patient variability in dose requirement, but also the within-patient variability, was similar for the two glycosides. However the digoxin used had a dissolution rate of over 90% in 1 h. When comparing medigoxin with digoxin of lower, or more variable dissolution rate, medigoxin may be preferable.
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  • 45
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    European journal of clinical pharmacology 18 (1980), S. 423-428 
    ISSN: 1432-1041
    Keywords: pyridostigmine ; myasthenia gravis ; pharmacokinetics ; bioavailability ; plasma levels
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of pyridostigmine was evaluated after intravenous injection in two healthy male volunteers and after oral administration to five subjects. Plasma concentrations of pyridostigmine were determined after ion pair extraction from plasma and analysis by gas chromatography — mass spectrometry with chemical ionization, using d6-pyridostigmine as internal standard. Degradation of pyridostigmine in vitro was compensated for by use of the deuterated internal standard and by rapid cooling and separation of plasma after blood sampling. After intravenous administration of pyridostigmine 2.5 mg the plasma elimination half-life was 1.52 h, the volume of distribution was 1.43 l/kg and the plasma clearance 0.65 l/kg × h. The pharmacokinetic constants were very similar after oral administration of pyridostigmine 120 mg; the elimination half-life was 1.78±0.24 h, the volume of distribution 1.64±0.29 l/kg and the plasma clearance was 0.66±0.22 l/kg × h. The bioavailability was calculated to be 7.6±2.4%. When pyridostigmine was taken together with food, the time to reach the peak plasma concentration was prolonged from 1.7 to 3.2 h. Bioavailability, however, was not influenced by concomitant food intake. “Steady-state” plasma concentrations of pyridostigmine were measured in myasthenic patients on their ordinary dose schedule of cholinesterase inhibitor drugs. More than a seven-fold difference in steady-state plasma concentration was found between patients taking approximately the same daily dose of pyridostigmine.
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  • 46
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    European journal of clinical pharmacology 21 (1982), S. 343-350 
    ISSN: 1432-1041
    Keywords: orphenadrine ; single dose ; multiple doses ; bioavailability ; pharmacokinetics ; N-demethylorphenadrine ; metabolism ; dog ; man
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Plasma concentrations of orphenadrine were measured by a specific gaschromatographic method in 5 healthy male volunteers after a single oral dose of orphenadrine hydrochloride 100mg. The single dose pharmacokinetic profile of orphenadrine was evaluated from these data. The elimination half-life ranged from 13.2–20.1 h after the commercial tablet formulation. Plasma concentrations, determined in volunteers and patients under different conditions of repeated oral administration of the same formulation of orphenadrine hydrochloride exceeded the theoretical values, predicted from the single dose pharmacokinetics, by a factor 2 to 3. The elimination half-lives after discontinuation of treatment showed a 2 to 3-fold increase over the single dose values. This demonstrates a clear discrepancy between the multiple and single dose pharmacokinetics of orphenadrine. Experiments in dogs suggested competition for biotransformation between orphenadrine and its metabolite N-demethylorphenadrine. Product inhibition of this type could explain the observed discrepancy.
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  • 47
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    Keywords: indapamide ; bioavailability ; pharmacokinetics
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    Notes: Summary Two formulations of indapamide tablets (2.5 mg) were given as a 5.0 mg dose and the subsequent blood levels were compared to those obtained after administration of a 5.0 mg solution. The study was conducted as a randomized three-way crossover design using healthy male volunteers. The drug was well tolerated by all the subjects involved. The area under the blood concentration versus time curve, extrapolated to infinity was essentially the same for all three formulations (4.2, 4.7, and 4.4 µg-h/ml). Statistical comparison of the blood levels from the two tablets showed that one tablet had a significantly greater maximum blood concentration (263 vs 231 ng/ml) and a significantly shorter time of maximum blood concentration (2.3 vs 3.5 h). Cmax (333 ng/ml) and tmax (0.7 h) values for the solution were significantly higher than either tablet. The average half-life (β-phase) for all three formulations was 15 h, while the average systemic clearance was 20 ml/min. Indapamide has a low clearance rate and there was no evidence that the drug undergoes a first-pass effect.
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  • 48
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    European journal of clinical pharmacology 23 (1982), S. 59-64 
    ISSN: 1432-1041
    Keywords: morphine ; rectal administration ; i.m. administration ; gas chromatographic mass spectrometric analysis ; bioavailability ; plasma levels
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary 21 healthy women undergoing gynaecological operations received rectal premedication with morphine 0.3 mg/kg body weight. Plasma concentrations of morphine were followed for 4 h by a GC/MS technique. In most patients the peak plasma concentration was reached after 30 min; the mean peak plasma level of morphine was 18 ng/ml (range 8.5–57 ng/ml). The bioavailability of rectal morphine was determined in 6 patients, who received an i.m. injection of morphine at a second operation. The mean bioavailability of rectal morphine was 31% (range 12%–61%). None of the patients showed any clinical sign of respiratory depression, and there was no increase in end-tidal carbon dioxide tension measured in 5 patients operated under spinal block.
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  • 49
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    European journal of clinical pharmacology 23 (1982), S. 235-240 
    ISSN: 1432-1041
    Keywords: ergotamine ; pharmacokinetics ; migraine ; plasma drug levels ; i.v. administration ; i.m. administration ; bioavailability
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The kinetics of ergotamine has been investigated in migrainous patients using a new, specific, sensitive HPLC assay (detection limit 100 pg/ml plasma). 10 patients were given ergotamine tartrate 0.5 mg i.v. and 5 of them received the same dose i.m. 2–3 weeks later. Blood samples were collected for up to 54 h following administration and the plasma concentration were analysed. After intravenous administration the plasma ergotamine declined rapidly, with an initial distribution half-life of 3 min followed by a mean terminal half-life of 1.86 h (range 90–155 min). The mean total plasma clearance was 11.0 ml kg−1 min−1, and the volume of distribution (Vdβ ) was 1847.6 ml kg−1. Individual t1/2β showed a positive linear correlation with the individual Vdβ . The intramuscular absorption of ergotamine was rapid and maximum plasma levels were usually obtained 10 min following administration. The biological availability was incomplete and variable at 46.6% (range 28.3–60.8%).
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  • 50
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    European journal of clinical pharmacology 24 (1983), S. 127-136 
    ISSN: 1432-1041
    Keywords: statistical analysis ; nonparametric statistical methods ; bioavailability ; confidence interval ; ANOVA
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary For a two-way cross-over design, which appears to be the most common experimental design in bioavailability studies, 95%-confidence limits for expected bioavailability can be obtained by classical analysis of variance (ANOVA). If symmetry of the confidence interval is desired about zero (differences) or unity (ratios) rather than about the corresponding point estimator, Westlake's modification can be used. Two nonparametric methods and their adaptations to bioavailability ratios are reviewed, one based on Wilcoxon's signed rank test (Tukey), and the other on Pitman's permutation test. The necessary assumptions and the merits of these procedures are discussed. The methods are illustrated by an example of a comparative bioavailability study. A FORTRAN program facilitating the procedures is available from the authors upon request.
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  • 51
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    European journal of clinical pharmacology 24 (1983), S. 791-796 
    ISSN: 1432-1041
    Keywords: furosemide ; bioavailability ; diuretic effect ; urine sodium ; urine potassium ; power of ANOVA ; tablet formulations ; urinary flow rate ; normal volunteers
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The relative bioavailability and diuretic effect of 2 commercially available tablet preparations of furosemide 40 mg was examined in 10 healthy male volunteers. A close linear relationship between the urinary excretion rate of furosemide and the rate of sodium ion excretion in urine and/or flow rate of urine was demonstrated. There were no significant differences in the urinary excretion of furosemide, sodium and potassium ions or urinary volume following the oral doses. The difference in drug content affected the urinary recovery of furosemide over 24 h but had no effect on the pharmacological response. The analytical power of ANOVA using the various parameters of the responses to furosemide was no lower than when the parameters of urinary excretion of furosemide were used.
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  • 52
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    European journal of clinical pharmacology 25 (1983), S. 237-241 
    ISSN: 1432-1041
    Keywords: triamterene ; bioavailability ; pharmacokinetics ; metabolism ; hydroxy triamterene sulphate ; urinary excretion ; i.v. administration ; first-pass-effect
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary With a new formulation, which made intravenous infusion of triamterene (TA) possible, plasma levels and urinary excretion rates of TA and its main metabolite (OH-TA-ester) were measured in a randomized, cross-over trial in 6 healthy volunteers given triamterene 10 mg i.v. and 50 mg p.o. TA and OH-TA-ester were determined by densitometric measurement of native fluorescence after thin layer chromatography. Distribution volumes of the central compartment of TA and OH-TA-ester were 1.49 l/kg and 0.11 l/kg, respectively. Terminal half-lives were 255 min for TA and 188 min for OH-TA-ester after i.v. administration. For TA total plasma clearance was 4.5 l/min and renal plasma clearance 0.22 l/kg. The formation of OH-TA-ester was very rapid and the concentration of the metabolite exceeded that of TA at all times. After i.v. administration the urinary recovery of TA and OH-TA-ester was 4.4% and 50.9%, respectively. The bioavailability of TA was 52%, corresponding to absorption of 83%. TA is partly eliminated by a first-pass-effect. The main metabolite of TA is OH-TA-ester, which is pharmacologically active.
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  • 53
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    European journal of clinical pharmacology 25 (1983), S. 449-453 
    ISSN: 1432-1041
    Keywords: canrenone ; pharmacokinetics ; plasma level ; bioavailability ; urinary excretion ; spironolactone
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Five healthy male volunteers received canrenoate-K 200 mg (Sincomen® pro injectione) by intravenous injection and one week later spironolactone 200 mg (Sincomen®-100) orally. Plasma levels and urinary excretion of unchanged canrenone were determined up to 24 h by a specific HPLC method. Following intravenous administration, the maximum plasma level of 2066±876 ng/ml was found after 29±15 min and thereafter the concentration declined with a half-life of 3.7±1.2 h. Total clearance was 4.2±1.7 ml/min·kg. After oral ingestion, the maximum concentration of 177±33 ng/ml was observed at 4.4±0.9 h. The absolute bioavailability of canrenone was 25±9%. Within 24 h, respectively 0.4 and 0.6 mg, canrenone were excreted by the kidney after intravenous and oral administration. The half-life of elimination was 4.9±1.8 h (i.v.) and 3.9±1.2 h (p.o.).
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  • 54
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    European journal of clinical pharmacology 26 (1984), S. 513-520 
    ISSN: 1432-1041
    Keywords: xipamide ; electrolyte excretion ; bioavailability ; elimination ; extrarenal clearance ; chronic renal failure ; furosemide ; hydrochlorothiazide ; amiloride
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The effect of a single oral dose of 40 mg xipamide on urinary excretion of Na+, K+, Cl−, Ca2+ and Mg2+ in healthy subjects and in patients with varying degrees of renal impairment was compared with various conventional diuretics. Xipamide caused marked excretion of Na+ and Cl−, whereas the diuretic produced only moderate kaliuresis; urinary excretion of Ca2+ was increased in proportion to Na+, like the loop diuretics. Xipamide affected electrolyte excretion even in patients with a creatinine clearance below 30 ml/min, as do the loop diuretics, too. Therefore, the pharmacodynamic characteristics of xipamide are more like those of a loop diuretic than of a thiazide. Xipamide was good bioavailable, its t1/2β was 7 h and urinary recovery of the undegraded drug was 40% of the given dose. In renal insufficiency, t1/2β increased from 7 to only 9 h, yielding a moderate increase in the AUC. Urinary recovery of the drug was reduced in proportion to the reduction in the creatinine clearance of the patient. Therefore, significant extrarenal elimination of the diuretic must be postulated, which suffices to prevent significant drug accumulation in renal failure.
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  • 55
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    European journal of clinical pharmacology 27 (1984), S. 105-110 
    ISSN: 1432-1041
    Keywords: phenytoin ; epileptic women ; pharmacokinetics ; bioavailability ; pregnancy
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Five epileptic women needing to commence phenytoin therapy during pregnancy received a single intravenous and a single oral dose of phenytoin several days apart before starting regular intake of the drug. Plasma phenytoin concentration — time data were analysed by three different pharmacokinetic techniques. However assessed, the mean oral bioavailability of the drug proved to be about 90% of the intravenous bioavailability. This finding makes it unlikely that impaired bioavailability accounts for the increase in oral phenytoin dosage necessary in pregnancy to maintain plasma phenytoin concentrations at pre-pregnancy values. Phenytoin clearance in the pregnant subjects was approximately double the published values for phenytoin clearance in nonpregnant persons. This suggests that increased (metabolic) clearance accounts for the increased phenytoin dosage requirement of pregnancy.
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  • 56
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    European journal of clinical pharmacology 27 (1984), S. 595-602 
    ISSN: 1432-1041
    Keywords: furosemide ; bioavailability ; generic tablet formulations ; intrasubject variability
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Intrasubject variation in bioavailability (rate and extent) and disposition of furosemide 40 mg was investigated using a repeated, randomized, double-blind cross-over study in 8 healthy subjects. Two generic tablet formulations (Lasix and Furix) and intravenous furosemide were compared on 6 separate days. Extensive intrasubject variability after oral administration was observed in AUC, mean absorption time (MAT) and urinary excretion. The variability (error variance) within the dosage forms was as large as that between the two generics. These variations most probably depended on the absorption process, since the repeated i.v. doses showed only marginal intrasubject variability. Absolute bioavailability was 56% for Lasix and 55% for Furix (AUC). The range was 20 to 84% between individuals and the maximal range within one individual was 20 to 61%. Confidence interval and Bayesian analysis showed a high probability of non-equivalence not only between but also within the generics when the separate cross-over experiments were analyzed (8 observations). When extending the analysis to 16 observations, bioequivalence was demonstrated for the two generic tablets. Rate of absorption, quantified as MAT, was 128 min for Lasix and 98 min for Furix (16 observations). Since MAT was significantly longer (p〈0.001) than the mean residence time after the i.v. dose (57 min), absorption was evidently the rate-limiting step in the overall kinetics of oral furosemide. Intraindividual variation in absorption is a confounding factor in bioavailability studies of furosemide using limited numbers of subjects. This is important to consider when designing and evaluating bioavailability studies for drugs showing these variations.
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  • 57
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    European journal of clinical pharmacology 29 (1985), S. 193-197 
    ISSN: 1432-1041
    Keywords: Glibenclamide ; intestinal absorption ; small and large intestine ; bioavailability
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary In a study of eight volunteers and six patients, glibenclamide was placed at different sites of the gastro-intestinal tract under visual control. The dose was instilled once into the stomach and once into the duodenum of the eight volunteers in a randomized crossover design. The six patients underwent diagnostic colonoscopy, and the dose was placed into the ascending colon if pathological findings were not present. The area under the concentration-time curve, completed by extrapolation, and the mean residence time of the drug in the body were calculated. These pharmacokinetic characteristics were examined using a Jonckheere test for ordered alternatives and a Wilcoxon signed rank pair test. The means of the areas under the curve were 477±131 ng·h ml−1 for the stomach, 475±142 ng·h ml−1 for the duodenum and 486±301 ng·h ml−1 for the colon. The mean residence time changed from 2.67±0.35 h for the stomach to 2.42±0.48 h for the duodenum and 3.55±0.68 h for the colon. These results indicate that although glibenclamide is absorbed from all three sites of the gastro-intestinal tract to the same extent, the rates of absorption are different. It is discussed whether these findings really confirm the pH-partition hypothesis in drug absorption. Since glibenclamide — a weak acid — has a pK-value of about 6.5, these data seem to confirm the pH-partition hypothesis of drug absorption.
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  • 58
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    European journal of clinical pharmacology 29 (1985), S. 251-253 
    ISSN: 1432-1041
    Keywords: paracetamol ; antacids ; acetaminophen ; bioavailability ; kinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The effect of two antacids on the bioavailability of paracetamol has been investigated in 12 young healthy volunteers. Following a random cross over design, each subject swallowed, on three separate occasions, one weak apart, 500 mg paracetamol alone, or together with two different aluminium hydroxide, magnesium hydroxide preparations (Dimalan and Maalox). Plasma paracetamol levels were measured by HPLC. The bioavailability of paracetamol was not altered by either antacid, but they both delayed the time to peak plasma concentration (0.85 h; 1.43 h; 1.25 h, without antacid, with Dimalan and with Maalox respectively). The peak plasma concentration was not affected by concurrent antacid administration.
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  • 59
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    European journal of clinical pharmacology 30 (1986), S. 407-416 
    ISSN: 1432-1041
    Keywords: malotilate ; cirrhosis ; bioavailability ; liver fibrosis ; metabolite kinetics ; pharmacokinetics ; portal-systemic shunting ; urinary metabolites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Malotilate, a sulphur-containing compound with antifibrotic and hepatoprotective properties in several animal models, has been investigated in cirrhotic patients. Nine patients with cirrhosis of various aetiologies and severity, and 4 healthy volunteers, participated in a pharmacokinetic study. After a single dose of 500 mg malotilate p.o. peak malotilate plasma concentration measured by GC-MS was 35 times higher in patients (median 0.70 µg/ml) than in controls (median 0.019 µg/ml). The median apparent oral clearance was approximately 50 times lower in cirrhotics (median 2.2l/min) than in healthy volunteers (118l/min). The apparent oral clearance was significantly correlated with indicators of portalsystemic shunting, such as the 2-h postprandial serum bile acids and the bioavailability of oral nitroglycerine. Urinary output of the glucuronidated metabolite-(M3), measured by HPLC, was normal in patients, whereas recovery of metabolite-M6 (resulting from ring opening and loss of sulphur) was reduced. Six patients in an open 6-month trial received malotilate 200 mg t.i.d. for 2 months and 400 mg t.i.d. for 4 months. The thrombocyte count increased and serum ferritin level fell in all patients, and serum cholinesterase rose and IgA decreased in 5 of 6. The other indicators of liver function did not show a significant change. Dry skin was the only possible adverse effect. It is concluded that first-pass elimination of malotilate is dramatically reduced in cirrhotics, and that a smaller amount of the drug reaches the liver in such patients. Malotilate was well tolerated, even in patients with advanced disease.
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  • 60
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    European journal of clinical pharmacology 31 (1986), S. 177-182 
    ISSN: 1432-1041
    Keywords: glibenclamide ; bioavailability ; pharmacokinetics ; dissolution ; hypoglycaemia ; healthy volunteers
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary A study has been carried out investigating four different marketed oral preparations of glibenclamide, correlating the effectiveness of the drug in these preparations in lowering plasma glucose concentrations with (i) the in vitro dissolution of the drug, measured by the British Pharmacopoeal and Desaga methods, and (ii) the in vivo bioavailability, assessed in 12 healthy human volunteers. The two dissolution methods yielded different rank orders of ease of dissolution of the drug from the various preparations; the findings of neither dissolution method correlated adequately with the results of the in vivo bioavailability studies, which correctly predicted the abilities of the preparations to reduce plasma glucose concentrations. Relative to an oral glibenclamide solution the bioavailabilities of the drug from three tablet preparations were 0.69, 0.49 and 0.24. The mean elimination half-life of the drug was 1.5 h and assuming complete bioavailability of the drug from oral solution the mean systemic clearance was 0.095 l kg−1h−1, and the mean apparent volume of distribution was 0.20 l kg−1. It is concluded that it may be unsafe to use in vitro dissolution data as a basis for assessing the bioequivalences of different glibenclamide preparations intended for oral use.
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    European journal of clinical pharmacology 18 (1980), S. 415-418 
    ISSN: 1432-1041
    Keywords: diclofenac ; acetyl salicylic acid ; intravenous bolus administration ; oral administration ; interaction ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Previous studies have shown that aspirin interacts with orally administered diclofenac sodium, causing reduced peak concentrations, lower levels and decreased areas under curves. In this study, diclofenac sodium was administered orally and intravenously with and without aspirin, to 6 healthy female volunteers. After intravenous dosing both plasma levels and areas under curves were significantly reduced although none of the rate constants was affected. The volume of distribution of diclofenac was increased as was the plasma clearance. Oral administration with aspirin also resulted in lower plasma levels, particularly peak levels, and areas under curves. Comparison of AUC's for both modes of administration with and without aspirin suggested that lower levels after oral administration were not due to impaired absorption. These observations are best explained by decreased protein binding and increased biliary excretion of diclofenac in the presence of salicylate.
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  • 62
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    European journal of clinical pharmacology 17 (1980), S. 309-315 
    ISSN: 1432-1041
    Keywords: valproic acid ; sodium valproate ; suppositories ; micro-enemas ; steady-state concentration ; absorption ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Rectal and oral absorption of valproic acid and its sodium salt by man were compared to explore the possibility of rectal administration of the drug. The plasma concentration of valproic acid was measured by gas chromatography after a single oral dose of sodium valproate 600 mg, and after single rectal doses of sodium valproate 600 mg and valproic acid 520 mg, in a cross-over study in 7 volunteers. The rectal dosage forms included fatty suppositories and aqueous solutions. Compared with oral administration, rectal absorption of sodium valproate from an aqueous micro-enema was fast and complete. The free acid was absorbed more rapidly from fatty suppositories than was the sodium salt. The absorption rate from the rectum increased with the dose of valproic acid. Both findings are consistent with a diffusion — absorption mechanism based on the pH-partition hypothesis. Differences in the chemical composition of the fatty suppository base were not reflected in differences in absorption rate and relative bioavailability. No essential difference in absorption rate was observed if volunteers remained lying or sitting during the experiment. Rectal dosing with valproic acid 520 mg dissolved in 4 ml suppositories, twice a day resulted in steady-state plasma concentrations of 50 to 100 µg · ml−1, within the therapeutic range.
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    European journal of clinical pharmacology 17 (1980), S. 379-384 
    ISSN: 1432-1041
    Keywords: theophylline ; aminophylline ; obstructive lung disease ; microcrystalline ; bioavailability ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Variation in the systemic disposition of theophylline after ingestion of a new microcrystalline product (Theolair®) has been investigated in 7 hospitalized patients with generalized obstructive lung disease. Disposition (absolute bioavailability) was determined by comparing in the same patients the areas under the serum concentration-time curves after a single oral dose of microcrystalline theophylline and after an intravenous infusion of aminophylline. Oral absorption appeared to be fast. The half-life of absorption was 19±9 min (mean±SD). Maximal serum concentrations reached after 100±30 min were found to be in a rather narrow range: 9.8±2.5 mg · 1−1. The absolute bioavailability of the microcrystalline preparation was high and it showed only small variation: 102.7±10.2% of the dose. Relevant pharmacokinetic parameters (half-life of elimination, volume of distribution and total body clearance) were determined after both routes of administration. Individual dosage regimens required to obtain a therapeutic serum concentration were calculated for each individual patient on the basis of the observed pharmacokinetic parameters.
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    European journal of clinical pharmacology 19 (1981), S. 53-55 
    ISSN: 1432-1041
    Keywords: digoxin ; bioavailability ; dose-dependency ; urinary excretion ; healthy volunteers
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Nine healthy volunteers received single 0.25, 0.5, 1.0, 1.5, and 2.0 mg doses of oral digoxin tablets in random sequence on five occasions separated by at least 4 weeks. Urinary excretion of immunoassayable digoxin was determined from 8 consecutive 24 h urine samples collected after each dose. Mean values of cumulative urinary excretion of digoxin at the 5 doses were: 40.9, 35.6, 36.4, 34.1, and 33.5% of the dose (F=0.64; d. f.=4.32; N. S.). Mean values of urinary excretion half-life were: 2.48, 2.03, 2.20, 2.07, and 1.87 days (F=2.87; d. f.=4.32;p=0.05). Thus, the bioavailability of orally administered digoxin tablets in healthy volunteers is dose-independent over an 8-fold range of doses.
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  • 65
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    European journal of clinical pharmacology 19 (1981), S. 287-292 
    ISSN: 1432-1041
    Keywords: diacetolol ; acebutolol ; bioavailability ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics and bioavailability of diacetolol, the principal metabolite of acebutolol, were studied in 6 healthy subjects. Plasma concentrations were determined following a single intravenous injection of diacetolol 100 mg and three oral doses of diacetolol 100, 400 and 800 mg, in random order. The average oral bioavailability of diacetolol was F: 0.302±0.052 (100 mg), 0.363±0.052 (400 mg) and 0.426±0.068 (800 mg); the differences are not significant. The mean plasma half-life of the terminal phase, 7.94±0.26 h after intravenous administration, was significantly higher than after oral administration 12.27±1.00 h (100 mg), 12.82±1.59 h (400 mg) and 13.05±1.22 h (800 mg) (p〈0.02 to 0.05); the mean urine half-lives of the terminal phase were not significantly different. Renal clearance of diacetolol 10.2±0.81·h−1 represented about two-thirds of total body clearance 15.9±1.21·h−1. The results suggest either a first-pass effect or incomplete absorption of diacetolol after oral administration.
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  • 66
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    European journal of clinical pharmacology 19 (1981), S. 305-307 
    ISSN: 1432-1041
    Keywords: ketoprofen ; aluminium phosphate ; bioavailability ; antacid ; pharmacokinetics ; interaction study
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The purpose of this study was to determine whether a concomitant single dose of antacid (aluminium phosphate), or multiple doses of this antacid, administered prior to and with ketoprofen would alter the bioavailability of this non steroidal anti-inflammatory agent. The possible effects of aluminium phosphate were evaluated following administration of ketoprofen alone (Phase I), co-administration of antacid and ketoprofen (Phase II), and antacid for four days before administration of ketoprofen with co-administration on the day of the study (Phase III). There were no significant differences between treatment means for peak plasma concentration, time to peak plasma concentration, and area under the plasma concentration-time curve. The observed differences were due only to individual effects. The results indicate a lack of interaction between ketoprofen and the antacid aluminium phosphate (Phosphalugel)
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  • 67
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    European journal of clinical pharmacology 19 (1981), S. 359-365 
    ISSN: 1432-1041
    Keywords: tolfenamic acid ; anti-inflammatory agent ; human pharmacokinetics ; bioavailability ; intravenous administration
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of tolfenamic acid, a new anti-inflammatory agent was studied in six healthy volunteers after an intravenous dose of 100 mg and oral doses of 100, 200, 400 and 800 mg. The disposition of intravenous tolfenamic acid could be described by two-compartment open model, with a central compartment volume (Vdc) of 5.6±0.31 (mean±SE), volume during β-phase (Vdβ) of 31±21, and a total elimination rate constant (k10) 1.6±0.1 h−1. The terminal elimination half-life was 2.5±0.6 h and the total plasma clearance 155±15 ml/min. The elimination occured principally by extrarenal mechanisms, the recovery of unchanged drug together with is glucuronide in urine averaging only 8.8% of the intravenous dose. The binding of tolfenamic acid to plasma proteins averaged 99.7%. The gastrointestinal absorption had a mean half-life of 1.7±0.1 h. Based on comparison of areas under the plasma concentration time-curves after intravenous and oral administration, the biovailability of tolfenamic acid capsules averaged 60%. The rate and extent of absorption and the rate of elimination of tolfenamic acid were independent of dose.
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  • 68
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    European journal of clinical pharmacology 21 (1982), S. 293-301 
    ISSN: 1432-1041
    Keywords: metipranolol ; deacetyl metipranolol ; pharmacokinetics ; bioavailability ; healthy volunteers
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetic parameters of deacetyl metipranolol were determined after i.v. infusion of increasing doses (6–25 mg) in 17 normal volunteers. In a second cross-over trial, deacetyl metipranolol 10 and 20 mg were infused in a further 10 subjects, and in a third trial another 20 volunteers received metipranolol 40 mg orally. Metipranolol is very rapidly and completely deacetylated in man, so all pharmacokinetic data refer to deacetyl metipranolol, which was assayed by gas chromatography-mass spectrometry. The pharmacokinetic analysis was performed using a recently developed model, using a volume of distribution which is variable with time. The following data were obtained after oral administration: (mean values); lag-time 7.3 min; tmax 50 min, invasion half-life 6.3 min; elimination half-life 3 h; urinary excretion of unchanged drug approximately 4% of the dose. The experiments with infusion of increasing doses, as well as the cross-over study with 10 and 20 mg i.v., showed dose-linearity of the kinetics. The respective mean half-lives of elimination were 2.6, 2.9 and 2.8 h. The mean total, renal and extra-renal clearances amounted to 1237 ml/min, 149 ml/min and 1068 ml/min, respectively. The distribution coefficient was 3.5 l/kg, and protein binding amounted to 70% within the range of therapeutic concentrations. Absolute bioavailability was found to be approximately 50% by several different evaluation procedures. Thus, the pharmacokinetic profile of metipranolol shares features of both the lipophilic and the hydrophilic groups of β-blocking agents.
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  • 69
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    European journal of clinical pharmacology 20 (1981), S. 65-72 
    ISSN: 1432-1041
    Keywords: tranexamic acid ; pharmacokinetics ; bioavailability ; oral absorption ; influence of food ; plasma clearance
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Tranexamic acid 1 g was given intravenously to three healthy volunteers. Plasma concentrations decayed in three monoexponential phases. Most elimination took place during the first eight hours, giving an apparent elimination half-life of approximately two hours. Plasma clearance ranged between 110–116 ml/min. The urinary recovery of tranexamic acid exceeded 95% of the dose. Ten healthy volunteers were given tranexamic acid 2 g orally on an empty stomach, and together with a meal. Food had no influence on the absorption of tranexamic acid, as judged by comparison of the peak plasma concentration, the time required to reach the peak, the AUC from zero to six hours, and the urinary excretion data. The oral bioavailability of tranexamic acid, calculated from 24 h urinary excretion after oral and intravenous administration, was 34% of the dose.
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  • 70
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    European journal of clinical pharmacology 22 (1982), S. 171-173 
    ISSN: 1432-1041
    Keywords: theophylline ; neonates ; bioavailability ; food intake ; premature infants
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary 16 premature infants suffering from neonatal apnoea received orally an aqueous solution of theophylline 5 mg/kg bodyweight under fasting conditions and immediately before a milk feed. Bioavailability up to 7 h after administration was determined from the serum concentration-time course. The rate of absorption was significantly decreased if the drug was given with food; mean maximum serum concentrations were reached after 4.7 h instead of 1.6 h under fasting conditions. The area under the curve did not differ between the two patient groups which indicates that only the rate but not the amount of absorption was affected by food intake. The influence of feeding on the rate of absorption of theophylline by premature infants, which is more pronounced than in adults, can be related to particular functional factors in the gastrointestinal tract during the neonatal period.
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  • 71
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    European journal of clinical pharmacology 22 (1982), S. 309-314 
    ISSN: 1432-1041
    Keywords: acetylsalicylic acid ; salicylic acid ; dipyridamol ; bioavailability ; kinetics ; rapid- and slow-release formulations
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Acetylsalicylic acid (ASA) is a strong, irreversible inhibitor of platelet aggregation, but loses this activity following first-pass deacetylation to salicylic acid (SA). In order to compare the bioavailability of unchanged ASA from rapid- and slow-release formulations, the single-dose concentration profiles of ASA and SA were studied in healthy volunteers following intake of two different rapid-release (conventional and effervescent tablets) and three different slow-release (microencapsulated ASA in tablets and in capsules, and enteric-coated tablets) formulations of ASA, and of one slow-release formulation of sodium salicylate. Since anti-platelet therapy with ASA is often combined with dipyridamol, the influence of this drug was also examined. The concentrations of ASA and SA were measured by high-pressure liquid chromatography. While the bioavailability of SA from the 5 ASA formulations was essentially equal and similar to that of the salicylate formulation, the bioavailability and peak concentrations of ASA appeared to be the much greater after rapid-release than after slow-release formulations. Indeed, ASA was only rarely detected in systemic blood following intake of slow-release ASA. Co-administered dipyridamol did not significantly influence the kinetics of ASA or SA. It appears that rapid-release formulations of ASA should be prefered in anti-platelet therapy, either alone or in combination with dipyridamol.
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  • 72
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    European journal of clinical pharmacology 20 (1981), S. 277-282 
    ISSN: 1432-1041
    Keywords: dexamethasone phosphate ; dexamethasone sulphate ; intravenous injection ; bioavailability ; pituitary-adreno-cortical suppression ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The metabolic fate and ACTH-supressant activity of two injectable dexamethasone esters, 21-phosphate and 21-sulphate, were studied in healthy men. After i.v. injection of 20 mg free steroid alcohol, dexamethasone phosphate was efficiently hydrolyzed to free dexamethasone, reaching its peak plasma concentration within 5 min. About 9% of the administered dose appeared in the urine as free dexamethasone. By contrast, virtually no free dexamethasone was found in plasma and urine after injection of dexamethasone sulphate. Pharmacokinetic analysis showed that dexamethasone sulphate had a shorter plasma half-life and a higher metabolic clearance rate than free dexamethasone. A larger fraction (60%) of dexamethasone sulphate was rapidly excreted unmetabolized in urine. The plasma cortisol level was significantly suppressed for more than 24 h after dexamethasone phosphate, while the plasma cortisol profile after dexamethasone sulphate merely showed physiological circadian variations. When the steroid esters were injected after pretreatment with metyrapone, a definite suppression of plasma ACTH was noted after dexamethasone phosphate, but again, dexamethasone sulphate was ineffective. These results cast serious doubt on the clinical value of dexamethasone sulphate as an injectable glucocorticoid, and critical reevaluation of this preparation is needed.
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    European journal of clinical pharmacology 24 (1983), S. 103-108 
    ISSN: 1432-1041
    Keywords: dexamethasone ; bioavailability ; pharmacokinetics ; ‘first-pass’ effect ; pre-systemic elimination
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics and oral biovailability of dexamethasone were studied in 6 patients with neurological disease being treated with high dosages of the drug. A specific high performance liquid chromatographic assay was used to measure dexamethasone concentrations. Unlike the previously published mean figure of 0.78 for the oral bioavailability of the drug given in single doses to healthy volunteers, the mean bioavailability of dexamethasone in the patients studied was 0.53±SD 0.40. It appeared more likely that this incomplete bioavailability was due to presystemic elimination than to poor absorption. The intravenous clearance of the drug was relatively high (0.4902±SD 2291 l kg−1, approximately 65% of expected hepatic plasma flow), the oral clearance higher (2.5804±SD 3.2181 l kg−1 h−1) while the absorption rate constant (4.8729±8.4998 h−1), suggested rapid absorption after oral administration. Prior phenytoin and possibly prior dexamethasone therapy is likely to have contributed to the higher clearance values of the drug in these patients than the values reported in healthy volunteers after single dose studies.
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    European journal of clinical pharmacology 20 (1981), S. 465-471 
    ISSN: 1432-1041
    Keywords: metoclopramide ; pharmacokinetics ; bioavailability ; first-pass effect
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The time courses of plasma metoclopramide concentrations were followed in six subjects after oral and intravenous single dose administration. Plasma concentration-time data following i.v. administration in each subject were found to fit a two compartment model with a mean terminal half-life of 4.55 h±0.80 h and a mean distribution half-time of 0.35 h±0.09 h. Volumes of distribution were high (3.43±1.181 · kg−1), and clearances (0.53±0.191 · kg−1h−1) approached liver plasma flow. This suggests that metoclopramide occurs at higher concentrations in tissues than in plasma, and that its clearance is probably limited by liver blood flow rather than liver metabolic capacity. The post-absorption decline in metoclopramide plasma levels after oral administration was also biexponential in each subject. The terminal half-life was 5.17 h±0.98 h. Mean volume of distribution and mean clearance were similar to intravenous values (after adjustment for bioavailability). Oral absorption was rapid with peak plasma concentrations being reached at a mean time of 0.93 h. A mean bioavailability of 0.77 was calculated for the six subjects, and it was postulated that this incomplete availability is due to a first-pass effect. The inter-individual variation in the degree of ‘first-pass’ was considerable (0.47–1.14).
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    European journal of clinical pharmacology 20 (1981), S. 473-478 
    ISSN: 1432-1041
    Keywords: methadone ; bioavailability ; pharmacokinetics ; single dose ; stable isotope technique ; two compartment model
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The disposition of methadone was studied in eight opiate dependent subjects during detoxification. Plasma concentrations were determined by mass fragmentography for 48 hours after administration of methadone 20 mg as tablets and simultaneous intravenous injection of deuterium-labelled methadone 20 mg. Pharmacokinetic parameters were calculated for the intravenous dose assuming a two compartment open model. Bioavailability was determined by comparing the areas under the plasma concentration versus time curves of unlabelled and labelled methadone. The beta-phase plasma half-lives varied five-fold, with a range from 8.5 to 47 h. The apparent volumes of distribution varied from 2.1 to 5.61/kg. Five patients had a bioavailability exceeding 90%, and three had lower bioavailabilities of between 41 and 76%. The unlabelled and labelled drug appeared to be pharmacokinetically equivalent. The data show that for a majority of these subjects the bioavailability was higher than 45%, the previously reported value. The marked individual variation in methadone pharmacodynamics and kinetics, and the possibilities both of cellular and methabolic tolerance, require an individually optimized dosage regimen.
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  • 76
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    Keywords: oxmetidine ; pharmacokinetics ; bioavailability ; plasma half-life ; clearance ; oral dose ; i.v. dose
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The plasma concentration curves and urinary excretion of oxmetidine after administration of single i.v. (100 mg) and oral (200 mg) doses have been studied in 11 patients with peptic ulcer disease. The mean bioavailability of the drug was 70% (range 53–91%). After intravenous administration, the mean plasmat 1/2β was 3.0 h, the mean apparent volume of distribution 0.7 l/kg, the mean total plasma clearance 12.3 l/h and the mean plasma renal clearance was 0.7 l/h. Following intravenous and oral administration an average of 6% and 3%, respectively, of unchanged drug was found in the urine. The plasma concentration curve after oral administration in most patients exhibited two maxima, with peak concentrations appearing between 45 and 210 min after dosing.
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  • 77
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    European journal of clinical pharmacology 22 (1982), S. 85-90 
    ISSN: 1432-1041
    Keywords: lignocaine ; verapamil ; propranolol ; bioavailability ; predictions ; first pass effect ; oral clearance
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary For drugs with a high hepatic clearance, bioavailability is low due to the so-called “first pass effect”. Prediction of the bioavailability for these drugs has been only lossely tested. It is proposed that by plotting the reciprocal of bioavailability versus the oral clearance, a straight line with intercept of unity and slope of reciprocal of hepatic blood flow should ensue. For lignocaine and verapamil, this relationship was found to be strong and gave good predictability, whereas for propranolol this relationship was weak and gave poor predictability. The proposed method may be of value in determining whether the low bioavailability of a drug is due to hepatic first pass metabolism.
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  • 78
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    European journal of clinical pharmacology 25 (1983), S. 689-693 
    ISSN: 1432-1041
    Keywords: amiodarone ; bioavailability ; calculation ; linear pharmacokinetics ; absorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Methods for estimating the bioavailability of drugs with long elimination half-lives are examined. Provided both absorption and disposition are linear a simple linear regression method is developed which can be used to calculate bioavailability in situations where only an incomplete estimate of the area under the curve (AUC) is available. The regression method and the traditional method of comparing the AUC following an oral dose to the AUC following an i.v. dose were applied to simulated data. It was found that the AUC ratio method works well as long as absorption is complete within the time over which the AUC is computed. The regression method is less precise than the AUC ratio method but is more accurate for drugs with long absorption half-lives. When applied to published data on a beta blocker the two methods produced comparable results. The bioavailability of amiodarone in three human subjects was calculated to be 0.20, 0.44 and 0.98 using the regression method with similar results from the ratio method. It is not possible to estimate the clearance of amiodarone from single dose data.
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    European journal of clinical pharmacology 26 (1984), S. 405-407 
    ISSN: 1432-1041
    Keywords: theophylline ; drug absorption ; bioavailability ; food intake ; sustained-release preparations ; Theolin Retard
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The absorption of theophylline from a sustained release tablet preparation (Theolin® Retard 300 mg) was studied in 10 subjects both when fasting and immediately after a standardized breakfast. Intravenous aminophylline was used as the reference material. Food did not influence the absorption from Theolin Retard. The bioavailability was complete (93% after 30 h) both with and without food, and no difference was found in the time to peak of the plasma concentration curve (7 h), or the mean residence time (14 h). The absorption characteristics, with predominantly zero order kinetics, did not change with concomitant intake of breakfast.
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  • 80
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    European journal of clinical pharmacology 27 (1984), S. 111-114 
    ISSN: 1432-1041
    Keywords: chlorambucil ; chronic lymphocytic leukaemia ; phenylacetic acid mustard ; food intake ; pharmacokinetics ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The influence of food intake on the pharmacokinetics of chlorambucil (C) and its cytotoxic metabolite, phenylacetic acid mustard (PAM), has been studied in man after oral doses of chlorambucil. The administration of chlorambucil with food resulted in slower absorption than when fasting. However, the area under the plasma concentration-time curve (AUC) was unaffected. The mean ratio AUCPAM/AUCC was 2.8 (range 1.4–7.1) under fasting and 3.3 (range 1.3–7.4) under nonfasting conditions. The metabolite very probably plays an important role in the cytotoxic effects observed after administration of C, since calculations show that a major fraction of the metabolite is eliminated by alkylation reactions.
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  • 81
    ISSN: 1432-1041
    Keywords: nitroglycerin ; plasma concentration ; transdermal administration ; bioavailability ; pharmacodynamics ; healthy volunteers
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary In 6 healthy volunteers, intravenous infusions of nitroglycerin 4.8 and 10.6 µg/min yielded mean steady-state plasma concentrations of 0.5±0.02 and 0.82±0.04 ng/ml as determined by a gas chromatographic/mass spectrometric method. The plasma concentrations reached in the same subjects 17 h after application of Nitroderm TTS 5 and 10 with in vivo release rates of 3.7 and 5.7 µg/min were 0.28±0.01 and 0.37±0.01 ng/ml, respectively. Thus, 75% of the quantity of nitroglycerin released by the systems passed into the circulation. The inter-individual and intra-individual variations in plasma concentrations were similar for both modes of administration. The nitroglycerin-induced morphological changes in the fingerpulse wave were clearly dose-dependent, but it seems that this pharmacodynamic parameter is determined less by the plasma concentration than by the nitroglycerin content of the vascular wall.
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  • 82
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    European journal of clinical pharmacology 31 (1987), S. 733-736 
    ISSN: 1432-1041
    Keywords: meptazinol ; pharmacokinetics ; elderly patients ; healthy volunteers ; bioavailability
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary We have determined the pharmacokinetics of meptazinol after its intravenous and intramuscular administration in a crossover study in 7 elderly hospital in-patients (〉70 years), and have compared with the results from 14 healthy, young volunteers (ages 20–40 years). The systemic availability after i.m. administration was comparable to that after i.v. administration, a result consistent with the physicochemical properties of the drug. There was a slight, but statistically significant (p〈0.01) prolongation in t1/2z in the elderly (mean 2.93 h) compared with the young (mean 2.06 h). This was associated with a 25% lower clearance in the elderly rather than with any alteration in volume of distribution. However, these changes would not appear to be substantial enough to require a revised dosage recommendation for meptazinol for this age group.
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  • 83
    ISSN: 1432-1041
    Keywords: indomethacin ; lysine salt ; controlled release formulation ; plasma concentration ; bioavailability
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The bioavailability of a new controlled release formulation of indomethacin lysine salt in tablets was tested in 6 healthy humans against a conventional indomethacin lysinate formulation in capsules. Both contained 100 mg of the drug, i.e. 70 mg indomethacin. Peak plasma levels were lower and more lasting and the AUC was higher with the new controlled release formulation. The latter on average produced active plasma levels for 12 h, and so it can be recommended for twice daily administration.
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    Environmental management 7 (1983), S. 177-187 
    ISSN: 1432-1009
    Keywords: Nitrogen ; Model ; Agriculture ; Mass balance ; Ground-water ; Denitrification ; Immobilization ; Dry deposition ; Nitrogen fixation ; Nitrate ; Florida
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A detailed nitrogen budget was devised for agricultural activities in the Florida peninsula, based on routine data published by state agricultural agencies. The model demonstrates that important unmonitored fluxes of nitrogen can often be calculated by mass balance on individual model compartments, and that the reasonability of poorly quantified fluxes can be assessed. The results of such models can be very useful in designing and assessing the results of field experiments and in prioritizing environmental monitoring programs.
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  • 85
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    European journal of clinical pharmacology 28 (1985), S. 229-230 
    ISSN: 1432-1041
    Keywords: diazepam ; dipotassiumchlorazepate ; benzodiazepines ; bioavailability ; administration ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Dipotassium chlorazepate (DPC) and diazepam (DZM) were given i.m. and i.v. to 6 healthy volunteers in doses of 20 mg (48.9 µmol) DPC and 15 mg (52.0 µmol) DZM. The interval between the injections was at least 1 week. Plasma samples were analyzed for DPC and DZM by HPLC. The bioavailability of DPC and DZM after i.m. administration, determined from computer calculated AUCs, was 1.04 and 0.85, respectively.
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  • 86
    ISSN: 1432-1041
    Keywords: moclobemide ; Ro 11-1163 ; pharmacokinetics ; bioavailability ; MAO activity in platelets ; monoamine metabolites in urine ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The plasma concentrations of the MAO-inhibitor moclobemide (Ro 11-1163) were determined in six healthy male subjects after oral (tablets) administration. Effects on MAO activity in platelets and excretion of monoamine metabolites in urine were investigated. The design of the study was a double-blind cross-over study with single oral doses of placebo, 50, 100 and 200 mg of moclobemide. The elimination profile of the drug showed that the half life of the unchanged drug ranged between 1 and 2 h except in one subject with a half-life of about 4 h. The mean bioavailability calculated using flow model concepts was F=0.43 after 50 mg, F=0.47 after 100 mg and F=0.59 after 200 mg. The outlier with a t1/2 of 4 h was found to have a bioavailability of more than 0.80 after all 3 doses. The slightly increasing bioavailability with higher doses was interpreted as evidence of saturable hepatic first-pass elimination of the drug. MAO activity in platelets was measured before and 2, 6 and 24 h after drug administration. No inhibition of platelet MAO was obtained at any point in time or dose level, as to be expected since moclobemide preferentially inhibits MAO A. Urine excretion of the monoamine metabolites homovanillic acid (HVA), dihydroxyphenylacetic acid (DOPAC), 3-methoxy-4-hydroxy-phenylglycol (MOPEG) and 5-hydroxyindoleacetic acid (5-HIAA) was followed during 48 h after placebo, 50 and 200 mg of moclobemide. Time but not dose contributed significantly to the variability in excretion of the monoamine metabolites. An apparent reduction of HVA and DOPAC levels was obtained in the early phase after the administration of 200 mg of moclobemide. In 1 subject with a mild drug reaction a pronounced decrease in the levels of all the metabolites was obtained. In the other 5 subjects, the compound was very well tolerated with a few reported side-effects like increased activity, somnolence or sweatings. There was a slight but significant increase in blood pressure following 50 and 100 mg but not 200 mg of moclobemide.
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    European journal of clinical pharmacology 28 (1985), S. 53-59 
    ISSN: 1432-1041
    Keywords: furosemide ; respiratory failure ; furosemide glucuronide ; first-pass metabolism ; diuretic effect ; bioavailability ; food effect ; chronic treatment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The bioavailability and diuretic effect of furosemide 40 mg administered orally for at least 6 months have been compared in patients with chronic respiratory failure and in healthy controls. The mean urinary recovery of unchanged drug was 11.5 mg and 9.41 mg in 24 h after pre- and postprandial administration to 10 patients, whereas the recovery was 14.4 mg in 10 healthy subjects. The diuretic effect, in terms of urine flow and sodium ion excretion in the 6 h after administration, was also less in patients than in healthy subjects. This was ascribed to the lower bioavailability of furosemide in patients, based on the urinary recovery of unchanged drug, and not to a lower level of response to furosemide than in healthy subjects. The mean absolute bioavailability of furosemide in 6 patients was 41.3% and 63.4%, respectively, calculated from unchanged drug and total drug (unchanged plus glucuronide conjugate). Approximately 53.9% of the dose of furosemide was excreted as the glucuronide conjugate after oral administration, and 34.2% after i.v. injection in the 6 patients. In 3 of the 6 patients studied, a distinct first-pass effect for glucuronidation of furosemide was observed after oral administration. In another study, the mean glucuronide fraction recovered in 24-h urine was 20.7% and 7.3% (p〈0.01) in 38 patients and 12 healthy subjects, respectively. The fraction in urine was not affected by changing the dose of furosemide from 20 to 120 mg. The lower bioavailability in patients as compared to healthy subjects is ascribed to enhanced glucuronidation and incomplete drug absorption.
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  • 88
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    European journal of clinical pharmacology 28 (1985), S. 85-88 
    ISSN: 1432-1041
    Keywords: bioavailability ; distribution-free statistical method ; confidence limits
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The confidence interval approach to bioavailability assessment depends first on selection of the confidence level, usually 95%, and then determination of the confidence limits for the expected bioavailability ratio AUC(Test)/AUC(Reference). In practice, however, it is sometimes of greater interest to know the probability that the expected bioavailability will fall below a critical value, for example 0.75, or within a clinically set bioequivalence range, for example 0.80 to 1.25. Up to now, posterior probability distributions have been suggested, based on classical analysis of variance (ANOVA) with its rather restrictive assumptions, including that of a (logarithmic) normal distribution. In this report, a distribution-free confidence interval based on the Wilcox-on signed-rank statistic has been generalized so that confidence probabilities can be obtained for any given confidence limits. In the case of unimodal and almost symmetrical sampling distributions, the results obtained are very similar to those of the ANOVA-based posterior probability distribution. However, skewed or multimodal sampling distributions are better reflected by the proposed distribution-free method, and more valid information is obtained in these cases, as demonstrated by examples.
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  • 89
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    European journal of clinical pharmacology 17 (1980), S. 375-378 
    ISSN: 1432-1041
    Keywords: mebendazole ; echinococcosis ; bioavailability ; absorption ; concomitant eating ; plasma level
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary High oral doses of mebendazole are used experimentally for the treatment of human alveolar and cystic echinococcosis. In order to assess bioavailability of this drug 1.5 g doses were given to 3 volunteers. Measurable plasma concentrations of 17 to 134 nmol/l were found only if mebendazole was given together with a fatty meal. In a patient with cholestasis plasma concentrations were higher than in the 3 normal subjects. In patients on long term treatment the increase in plasma concentration after administration of a 1 g dose varied between 0 and 500 nmol/l. It is concluded that systemic availability of mebendazole is enhanced by concomitant food intake. In view of the large intra- and interindividual variation in plasma concentration, monitoring plasma levels during long term therapy appears advisable.
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  • 90
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    European journal of clinical pharmacology 17 (1980), S. 465-468 
    ISSN: 1432-1041
    Keywords: paracetamol ; suppository ; tablets ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The relative bioavailability of a new paracetamol suppository (Panodil) and tablets in doses of 0.5 and 1 g was investigated in eight healthy subjects. The tablets were absorbed faster and higher peak plasma concentrations were obtained than after the suppositories. The bioavailability of the suppositories was approximately 80% of that of the tablets at both dose levels. There was no indication of capacity-limited elimination at either the two doses investigated.
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  • 91
    ISSN: 1432-1041
    Keywords: verapamil ; pharmacokinetics ; bioavailability ; hepatic first-pass metabolism ; stable isotopes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Following i. v. administration, the plasma concentration-time curve of verapamil could best be described by either a mono- or biexponential equation. Total plasma clearance (1.26 l/min) approached liver blood flow (1.5 l/min), so it can be concluded that its clearance is liver blood flow-dependent. Although absorption was almost complete after oral administration, absolute bioavailability (20%) was low, due to extensive hepatic first-pass metabolism. The approach using stable isotope-labelled and unlabelled drug permits simultaneous administration by the intravascular and extravascular routes, thus allowing determination of absolute bioavailability in a single experiment.
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  • 92
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    European journal of clinical pharmacology 19 (1981), S. 149-155 
    ISSN: 1432-1041
    Keywords: proxyphylline ; asthma ; pharmacokinetics ; bioavailability ; healthy adults ; theophylline derivative
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Serum concentrations and urinary excretion of proxyphylline have been measured in five healthy adults after intravenous (29 µmol/kg), single oral (21 µmol/kg) and multiple oral (21 µmol/kg three times a day) doses to produce steady state. The mean peak time after oral administration was 29 min. The mean fraction absorbed was 1.09 calculated from serum concentrations, and 1.05 calculated from urinary excretion of the drug. The apparent volume of distribution was 0.61 l/kg (0.53–0.72 l/kg), 26% higher in males than in females. A two-compartment open model was found to describe the decline in the serum concentrations, giving a mean distribution half-life of 6 min. The intersubject ranges of biological half-life were 8.1–12.1 h and 8.3–12.6 h calculated from serum and urine data, respectively. 24% (18–29%) of the dose was excreted unchanged in urine, which agreed with the relationship between the calculated total body clearance and the renal clearance of the drug.
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  • 93
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    European journal of clinical pharmacology 19 (1981), S. 343-347 
    ISSN: 1432-1041
    Keywords: cimetidine ; phenobarbital ; gastro-intestinal absorption ; bioavailability ; renal clearance ; non-renal clearance ; enzyme induction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of orally administered cimetidine was studied in 8 healthy subjects before and after 3 weeks of treatment with phenobarbital 100 mg daily, and in a separate study 4 subjects received cimetidine intravenously before and after the administration of phenobarbital. There was no change in the volume of distribution, but total plasma clearance was increased by a mean of 18%, mainly due to a 37% increase in nonrenal clearance. Renal clearance and half-life were not significantly altered. The area under the plasma concentration-time curve after oral administration was significantly (P≪0.05) reduced by a mean of 15% after phenobarbital treatment. The amount of cimetidine excreted in urine and its sulphoxide metabolite were significantly (P〈0.05) reduced, on average by 34% and 26%, respectively by phenobarbital treatment. The data indicate that an apparent 20% reduction in the absorption of cimetidine was due to induction of gastrointestinal metabolism of cimetidine, with some contribution also from hepatic metabolism. Reduced absorption per se could not be totally excluded. Although the magnitude of the change was small, the finding of an 11% decrease in the time to achieve an effective plasma level of cimetidine after phenobarbital treatment may contribute to the ineffectiveness of cimetidine in certain patients.
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  • 94
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    European journal of clinical pharmacology 22 (1982), S. 359-365 
    ISSN: 1432-1041
    Keywords: chlorpheniramine ; pharmacokinetics ; oral absorption ; half-life ; bioavailability ; volume of distribution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Plasma and urinary levels of chlorpheniramine (CPM) and its 2 demethylated metabolites were measured by HPLC after i.v. and oral dosing. In 5 mg (maleate) i.v. bolus studies in 2 subjects, plasma CPM levels were fitted to triexponential equations with terminal half-lives (t 1/2) of 23 and 22 h and area of 3.6 and 3.21/kg, respectively. Intravenous data predicted hepatic blood extraction ratios for the 2 subjects to be 0.06 and 0.07, respectively. Absolute bioavailability from oral solution (10 mg) was 59 and 34%, and from tablets (8 mg) 44 and 25%, respectively, indicating extensive gut first-pass metabolism. Mean t 1/2 from 7 oral fasting studies in 5 subjects was 28 h (19–43 h). Mean absorption lag time was 0.7 h (0.4–1.3 h), and mean peak time was 2.8 h (2–4 h). In 2 subjects, 6 mg solutions were given every 12 h for 9 doses; good correlation between single and multiple dose kinetics was found. Significant accumulation was demonstrated in simulation studies with frequent daily dosing. Estimated accumulation ratios vary from 4.1 to 9.4 (mean 6.5). The t 1/2 from urinary data (collected for 12 days) was consistent with plasma data. The above results suggest the need to reexamine the current practice of frequent daily dosing and the use of sustained or controlled release dosage forms of this drug. The possible cause of reduced plasma clearance of CPM in renal patients is discussed.
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  • 95
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    European journal of clinical pharmacology 22 (1982), S. 459-462 
    ISSN: 1432-1041
    Keywords: tolbutamide ; diabetes ; food intake ; blood glucose ; blood insulin ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The effect of food on the rate and extent of absorption of tolbutamide in diabetic patients was studied by varying the time of drug administration in relation to the ingestion of a standard meal. Serum levels of tolbutamide, insulin and glucose and related bioavailability parameters were compared following the administration of a single dose of tolbutamide 0.5 g to diabetic patients 30 min prior to and immediately before a standardized meal. A placebo dosage form was also administered to determine baseline glucose and insulin response to the meal. The 700 calorie standard meal was composed of 41% carbohydrate, 18% protein, and 41% fat. Administration of the drug with the meal resulted in a 6% (statistically significant) decrease in the extent of absorption, as determined by measurement of the area under the tolbutamide serum level-time curve from zero to infinity. Serum levels of tolbutamide were also significantly higher 0.5 h after drug administration when the drug was taken with the meal. Except for these two minor effects, no other differences between the drug treatments were observed in any other parameters of tolbutamide absorption or in the postprandial glucose and insulin serum levels. Therefore, the small differences found were judged to be clinically meaningless. These findings demonstrate that administration of tolbutamide 0.5 g tablets 30 min prior to or with a standard meal results in equivalent therapeutic actions.
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  • 96
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    European journal of clinical pharmacology 23 (1982), S. 87-92 
    ISSN: 1432-1041
    Keywords: phenobarbital ; epilepsy ; kinetics ; bioavailability ; epileptic patients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The kinetics of phenobarbital (PB) were evaluated in six normal subjects and six epileptic patients treated with phenytoin or carbamazepine. Each normal subject received three single doses of PB: PB-sodium 130 mg i.v. (IV), PB sodium 130 mg i.m. (IM), and PB acid 100 mg orally (PO), in random order at least one month apart. After IV PB distributive half-lives varied from 0.13 to 0.70 h, disposition half-lives were 75 to 126 h, steady state volume of distribution (Vss) was 0.54±0.03 l/kg, and clearance (CL) was 3.8±0.77 ml/h/kg. Absolute bioavailability of IM PB was 101±13%, of PO PB (corrected for dose) 100±11%. Peak serum PB concentrations were achieved from 2 to 8 h after IM administration, and from 0.5 to 4 h after PO administration. Epileptic patients exhibited similar PB kinetics: disposition half-lives were 77 to 128 h, Vss 0.61±0.05 l/kg, and Cl 3.9±0.76 ml/h/kg. Phenobarbital appears to represent an exception among antiepileptic drugs, in that pharmacokinetic data obtained in normals can reasonably be extrapolated to the epileptic population.
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  • 97
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    European journal of clinical pharmacology 23 (1982), S. 271-273 
    ISSN: 1432-1041
    Keywords: chloroquine ; bioavailability ; gastrointestinal absorption ; food effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The bioavailability of chloroquine in 7 healthy adult male volunteers was assessed with and without a standard breakfast. Chloroquine (600 mg base) was administered orally and timed blood samples were obtained for determination of plasma concentrations. The results suggest that the AUC and peak plasma levels were significantly higher when chloroquine was administered together with food, although the rate of absorption was not different. It appears, therefore, that food facilitates chloroquine absorption and the extent of absorption is significantly modified. Hence administration of chloroquine together with food appears to be an advisable clinical practice.
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  • 98
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    European journal of clinical pharmacology 20 (1981), S. 449-452 
    ISSN: 1432-1041
    Keywords: theophylline ; ethylenediamine ; suppository ; serum concentration ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The absorption of theophylline from a suppository not containing ethylenediamine was tested in 9 healthy volunteers. AUC after rectal administration of anhydrous crystalline theophylline 250 mg (AUCrectal) was compared with the AUC after oral administration of microcrystalline theophylline 250 mg (Nuelin®; AUCoral) in a randomized, cross-over study. The ratio AUCrectal/AUCoral was 0.75 at 10 h, and the ratio AUCrectal×βrectal/AUCoral×βoral extrapolated to infinite time was 0.83. A mean concentration of 5.7 µg/ml was reached 3.7 h after a single rectal dose. The absorption studies were performed with suppositories stored for 15 weeks at 22 °C. No effect on the in vitro release rate of theophylline from the suppository was observed during storage at room temperature from 3 to 31 weeks after production. Since aminophylline suppositories are known to decompose upon storage, the results suggest that a formulation without ethylenediamine is preferable for the rectal administration of theophylline.
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  • 99
    ISSN: 1432-1041
    Keywords: buflomedil ; vasodilatation ; pharmacokinetics ; bioavailability ; vasoactive drug
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary A dose-ranging pharmacokinetic study of buflomedil was carried out in eight subjects to determine the pharmacokinetic parameters of the drug after oral and intravenous administration. Based on AUC∞ analyses, the pharmacokinetics of buflomedil were found to be linear within the dose ranges studied (50 to 200 mg for i. v. injection and 150 to 450 mg for oral administration). In the oral study, the mean biological half-life of the drug was 2.97 h, while after intravenous dose it was 3.25 h. The apparent volume of distribution after the pseudodistribution equilibrium (Fdβ) and volume of distribution at the steady state (Vdss) were 1.43±0.24 l/kg and 1.32±0.26 l/kg, respectively. The mean urinary recovery of intact drug and the metabolite, paradesmethyl buflomedil, after intravenous dosing, were 23.6% and 18.7%, respectively, while after oral dosing, they were 18% and 14.8%, respectively. On the average, 72% of the dose was obserbed into the systemic circulation after oral administration. This level of bioavailability was attributed to the hepatic first-pass effect.
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  • 100
    ISSN: 1432-1041
    Keywords: chlorambucil ; prednimustine ; plasma concentrations ; bioavailability ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of chlorambucil has been investigated in a cross over study after oral administration of the free drug (10 mg) and its prednisolone ester (prednimustine, 100 mg). The bioavailability of chlorambucil was about five times lower when given as prednimustine as compared to administration of the free drug. The peak plasma concentration was about twice as high and it was obtained more rapidly when the free drug was given. No intact prednimustine could be detected in plasma.
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