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  • 1
    Electronic Resource
    Electronic Resource
    The influence of levodopa on gastric emptying in healthy elderly volunteers (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 409-412 
    Details
    ISSN: 1432-1041
    Keywords: Levodopa ; Gastric emptying ; paracetamol ; elderly subjects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Paracetamol absorption and 99Tc-DTPA measurements have been used to determine the influence of levodopa on gastric emptying in 8 healthy elderly volunteers. In the absence of levodopa 7 subjects showed a rapid gastric emptying pattern by gamma-camera and a single major peak in the plasma concentration-time curve of paracetamol. One subject showed two rapid phases of gastric emptying separated by a period of negligible emptying and had 2 separate peaks in the paracetamol plasma concentration-time curve. In the presence of levodopa, the gamma-camera data for 6 subjects showed a pattern of gastric emptying consisting of 2 rapid phases separated by a plateau. In each case secondary peaks in the plasma concentration-time curve of paracetamol occurred about 30 min after the end of the plateau. The time to 90% emptying on the gamma scan was increased significantly from 40 min to 65 min in the presence of levodopa. Comparison of the present data with those reported previously indicates that levodopa affects gastric emptying in the both elderly and young volunteers to a similar extent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00280127
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  • 2
    Electronic Resource
    Electronic Resource
    Factors affecting the pharmacokinetics of nifedipine (1987)
    Springer
    European journal of clinical pharmacology 32 (1987), S. 351-355 
    Details
    ISSN: 1432-1041
    Keywords: nifedipine ; cimetidine ; pharmacokinetics ; drug interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The plasma pharmacokinetics of nifedipine and the formation of its metabolites have been studied in volunteers under conditions which would affect the activity of the cytochrome P-450 system. The pharmacokinetics of a 10-mg capsule of nifedipine were not significantly different between smokers and non-smokers of similar age. After pretreatment with cimetidine, which inhibits the activity of cytochrome P-450, the peak plasma concentration and area under the plasma-time concentration curve for nifedipine were increased by a mean 84%. In contrast, pre-treatment with ranitidine which has little effect on cytochrome P-450, did not significantly alter nifedipine pharmacokinetics. Smoking does not contribute significantly to the variability in nifedipine pharmacokinetics. However, the interaction between nifedipine and cimetidine, but not ranitidine, may be of clinical importance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00543968
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  • 3
    Electronic Resource
    Electronic Resource
    The metabolism of antihistamines and drug interactions: the role of cytochrome P450 enzymes (1999)
    Oxford BSL : Blackwell Science Ltd
    Clinical & experimental allergy 29 (1999), S. 0 
    Details
    ISSN: 1365-2222
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The non-sedating antihistamines show a diversity of fates in the body and the parent drugs and metabolites may differ in their biological properties. Clinically significant interactions with inhibitors of cytochrome P450 have been reported primarily for terfenadine, which has the potential for cardiac toxicity, and is metabolized to fexofenadine, an antihistamine without cardiac effects. Astemizole shares many of these characteristics and important safety-related interactions are likely. Loratadine undergoes extensive metabolism so that pharmacokinetic interactions could occur, but they would be of little clinical importance because of the lack of cardiac activity of the parent drug and its metabolites. Ebastine also undergoes pharmacokinetic interactions, the significance of which is dependent on clarification of the extent of any relevant cardiotoxicity of both ebastine and its metabolite. Interactions would not be clinically important for cetirizine and fexofenadine which do not show cardiac effects and are eliminated with little metabolism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2222.1999.0290s3116.x
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  • 4
    Electronic Resource
    Electronic Resource
    Environmental carcinogens and large bowel cancer (1976)
    [s.l.] : Nature Publishing Group
    Nature 263 (1976), S. 234-235 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The conjugates and metabolites of benzo[a]pyrene were prepared biologically. This compound has been shown to undergo oxidation and conjugation in the rat and is excreted mainly in the bile as glucuronic acid and sulphate conjugates of phenols, as conjugates of dihydrodiols and possibly as ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/263234a0
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of Post-coital Unilateral Ovariectomy on Implantation in Mice (1968)
    [s.l.] : Nature Publishing Group
    Nature 219 (1968), S. 733-734 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Unilateral ovariectomy under ether or avertin anaesthesia was performed at varying times after coitus. Because of the known tendency in some strains of mice for greater numbers of eggs to be shed from the right ovary than from the left6, the operations were carried out on alternate sides. No ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/219733a0
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  • 6
    Electronic Resource
    Electronic Resource
    The influence of two types of meal on the pharmacokinetics of a modified-release formulation of nifedipine (Adalat Retard) (1997)
    Springer
    European journal of clinical pharmacology 53 (1997), S. 141-143 
    Details
    ISSN: 1432-1041
    Keywords: Key words Nifedipine; drug absorption ; food
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Objective: The effect of two different types of meal on the absorption of a modified-release formulation of nifedipine (Adalat Retard) was studied. Results: A light breakfast produced a delay in gastric emptying (indicated by the rate of paracetamol absorption) compared with the fasting state, but did not alter the tmax or Cmax for nifedipine significantly. After a cooked breakfast, there was less delay in gastric emptying and again no delay in tmax for nifedipine. However, the Cmax for nifedipine was significantly higher than in the fasting state. Neither meal influenced the bioavailability of nifedipine. Conclusion: The results suggest that the nature of the meal has an important influence on the absorption profile of this formulation of nifedipine, probably by an effect on its dissolution. This study illustrates the importance of considering the effects of different types of meal before concluding that food does not affect the pattern of drug absorption.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002280050352
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  • 7
    Electronic Resource
    Electronic Resource
    The pharmacokinetics of caffeine in Nigerian children suffering from malaria and kwashiorkor (2000)
    Springer
    European journal of clinical pharmacology 56 (2000), S. 153-158 
    Details
    ISSN: 1432-1041
    Keywords: Key words Caffeine ; Malaria ; Kwashiorkor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Objectives: Caffeine-containing beverages are generally consumed by Nigerians suffering from malaria and kwashiorkor in the belief that caffeine aids early recovery from these illnesses, which are common in the tropics. However, there are no studies on the influence of these diseases on the absorption and pharmacokinetics of caffeine in Africans. Materials and methods: A single oral dose of caffeine was given to five healthy children and to five and seven children suffering from malaria and kwashiorkor, respectively. Caffeine and its dimethylxanthine metabolites were measured in plasma using high-performance liquid chromatography. Results: The maximum plasma concentration (Cmax) of caffeine and the time of Cmax were similar (P 〉 0.05) in the three groups. However, the elimination half-life of caffeine was significantly longer in children with malaria (9.2 ± 3.5 h) (P 〈 0.01) and kwashiorkor (13.1 ± 7.9 h) (P 〈 0.05) than in the healthy controls (3.7 ± 1.8 h). The total plasma oral clearance of caffeine of 4.4 ± 1.9 ml/min/kg in healthy children was significantly higher (P 〈 0.01) than in those with kwashiorkor (2.0 ± 0.9 ml/min/kg) and malaria (1.6 ± 1.0 ml/min/kg) (P 〈 0.05). Paraxanthine was the principal metabolite in all the three groups with Cmax significantly higher in healthy children (1.3 ± 0.3 μg/ml) than in children with malaria (0.8 ± 0.4 μg/ml) (P 〈 0.05) and kwashiorkor (0.3 ± 0.1 μg/ml) (P 〈 0.0001). CYP1A2 activity, measured by the plasma ratios of paraxanthine: caffeine, was significantly lower in kwashiorkor and malaria. Conclusions: This study showed that the plasma kinetics of caffeine are significantly altered in malaria and kwashiorkor, and CYP1A2 activity was lower in these two disease groups.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002280050734
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  • 8
    Electronic Resource
    Electronic Resource
    The effects of acute falciparum malaria on the disposition of caffeine and the comparison of saliva and plasma-derived pharmacokinetic parameters in adult Nigerians (2000)
    Springer
    European journal of clinical pharmacology 56 (2000), S. 159-1065 
    Details
    ISSN: 1432-1041
    Keywords: Key words Pharmacokinetics ; Caffeine ; Malaria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Objectives: The pharmacokinetics of caffeine and its dimethylxanthine metabolites were evaluated in Nigerians, for whom it is normal to consume caffeine-containing beverages during ill health and recuperation in the belief that caffeine aids early recovery from illness; however, there are no data defining the kinetics of caffeine in healthy and ill Nigerians. Materials and methods: A single oral dose of 300 mg caffeine was given to ten healthy adult Nigerians and ten adults suffering from acute uncomplicated Plasmodium falciparum malaria infection. Caffeine and its dimethylxanthine metabolites were measured in plasma and saliva of healthy subjects and in plasma of patients suffering from malaria using high-performance liquid chromatography. Results: The plasma pharmacokinetics of caffeine per se in both groups was similar (P 〉 0.05). The maximum plasma concentration (Cmax) of paraxanthine was significantly lower (P 〈 0.05) in malaria (0.9 ± 0.4 μg/ml) than in healthy controls (1.4 ± 0.5 μg/m1), and the paraxanthine:caffeine area under the plasma concentration–time curve ratio, an index of cytochrome P450 (CYP)IA2 activity was significantly lower (P 〈 0.05) in malaria patients (0.5 ± 0.1) than in healthy controls (0.3 ± 0.2). The elimination half-life of theophylline was longer in malaria, while the area under the plasma concentration–time curve of theobromine was significantly higher (P 〈 0.05) in malaria (7.1 ± 3.4 μg ml−1 h) than in healthy adults (4.1 ± 2.2 μg ml−1 h). Excellent correlations were found between saliva and plasma concentrations of caffeine (r 2=0.98) with a mean saliva:plasma concentrations ratio of 0.7 ± 0.1. The plasma concentrations (Cmax and AUC) were therefore higher than the corresponding salivary levels, so that the apparent oral clearance calculated for saliva exceeded the true oral clearance based on plasma data. Conclusions: Acute Plasmodium falciparum malaria produced significant changes in the disposition of caffeine metabolites. Analysis of concentrations in saliva is a useful non-invasive method for monitoring the kinetics of caffeine and paraxanthine in Nigerians.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002280050735
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  • 9
    Electronic Resource
    Electronic Resource
    Inability of second trimester human amniotic fluid cell cultures to aromatize C19-steroids (1985)
    Springer
    Journal of inherited metabolic disease 8 (1985), S. 25-32 
    Details
    ISSN: 1573-2665
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Amniotic fluid (AF) and fibroblast (F) cell types, derived from human amniotic fluid by amniocentesis in the second trimester, were cultured using media of varying composition and their ability to transform C19-steroids to oestrogens was investigated by fluorimetry, radioimmunoassay, tritium release and measurement of cytochrome P450. Although the cells were shown to be metabolically active by the presence of mitotic figures, the incorporation of tritiated leucine into protein and the production of the β-subunit of hCG, no evidence of aromatization was obtained despite the inclusion in the medium of a number of steroids known to be transformed to oestrogens in severalin vivo andin vitro preparations. The addition of reported stimulants of aromatase activity, viz. hCG, FSH, diethylstilbestrol, prostaglandins E2 and F2α and dibutyryl cyclic AMP, was without effect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01805481
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