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  • 1
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    German Medical Science GMS Publishing House; Düsseldorf
    In:  Evidenz und Entscheidung: System unter Druck; 10. Jahrestagung des Deutschen Netzwerks Evidenzbasierte Medizin; 20090305-20090307; Berlin; DOC09ebmP4.1 /20090304/
    Publication Date: 2009-03-20
    Keywords: ddc: 610
    Language: German
    Type: conferenceObject
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  • 2
    ISSN: 0378-4347
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1041
    Keywords: sulphinpyrazone ; metabolism ; single dose ; chronic treatment ; pharmacokinetics ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of sulphinpyrazone and its major metabolites (sulfide, sulfone, p-hydroxysulfone and p-hydroxy-sulphinpyrazone) were investigated in 9 volunteers after a single oral dose as well as after chronic treatment for 23 days. Chronic administration of sulphinpyrazone, in comparison with a single oral dose, led to significant changes in plasma AUC (115.86 to 42.90 mg/l·h), in renal clearance (1.06 to 1.80l/h), in hepatic intrinsic clearance (319.0 to 598.0l/h), and in the unbound fraction in plasma 1.15 to 1.69%) and in tissue (2.73 to 1.31%). The volume of distribution changed from 20.24 to 52.041. The steady state concentrations predicted from the single dose were significantly higher than the values found after chronic treatment. The results suggest that sulphinpyrazone induces its own metabolism. The metabolism of the sulfone, p-hydroxysulfone and the p-hydroxy-sulphinpyrazone to further degradation products was also induced. Chronic treatment with sulphinpyrazone reduced the plasma AUC of the sulfide and caused a decrease in its elimination half-life (20.9 to 14.3 h). Since considerable amounts of the sulfide are formed in the G.I. tract, it is suggested that besides the induction of metabolism, bacteria which reduce sulphinpyrazone to the sulfide may also be responsible for the observed pharmacokinetic changes.
    Type of Medium: Electronic Resource
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  • 4
    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.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-1041
    Keywords: clonidine ; maprotiline ; interaction ; tricyclic antidepressants ; pharmacodynamic effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The well known interaction between tricyclic antidepressants and the centrally acting antihypertensive drug clonidine, namely impairment of the antihypertensive effect of clonidine, is thought to be related to blockade of noradrenaline uptake or competition at central alpha-receptors. The tetracyclic antidepressant maprotiline has been shown to be a potent inhibitor of noradrenaline uptake and it might, therefore, interfere with the antihypertensive action of clonidine. The possible interaction of clonidine and maprotiline was studied in 8 healthy subjects using doses in the therapeutic range. The study followed a double-blind, cross over design, in which clonidine alone (0.3 mg p.o.), clonidine (0.3 mg p.o.) plus maprotiline (100 mg in 4 divided doses over 22 h), maprotiline alone (100 mg in 4 divided doses over 22 h) and placebo were given by the double-dummy technique. Several pharmacodynamic parameters were measured for 12 h after administration of the drugs (supine and erect blood pressure, heart rate, saliva production and sedation). Concurrent administration of maprotiline did not alter the effect of clonidine and neither the size nor the time of the maximal response after clonidine were influenced by maprotiline. It is concluded that [1] blockade of noradrenaline uptake is not associated with the interaction of tricyclic antidepressants and clonidine, and [2] maprotiline should be preferred to tricyclic antidepressants in hypertensive patients on clonidine therapy if a concomitant depressive illness has to be treated.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-1041
    Keywords: theophylline ; furosemide ; drug interaction ; urinary flow ; renal clearance ; urinary excretion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary In new of previous contradictory results, the possible interaction between the loop diuretic furosemide and theophylline was re-evaluated in 12 healthy volunteers with a steady-state plasma theophylline level. Two doses of furosemide 20 mg at a 4 h interval did not influence the steady-state plasma concentration of theophylline despite causing a moderate diuresis. Urinary recovery of theophylline and its metabolites amounted to 106±21% of the dose without furosemide and 96±19% of the dose with furosemide, demonstrating that there was no influence on the enteral absorption of theophylline of the furosemide treatment. After the first dose of furosemide the fractional renal clearance (CLR1) of theophylline (fractional = hourly sampling period) changed in parallel with the urinary flow rate, without a significant difference between treatment with and without furosemide. After the second dose of furosemide, CLR1 was increased in the first hour and then it declined to levels far lower than the control value. This unexpected result could explain the unchanged plasma concentration of theophylline during furosemide treatment.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-1041
    Keywords: enoxacin ; theophylline ; drug interaction ; healthy volunteers ; adverse effects ; pharmacokinetics ; renal tubular excretion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The mechanism of the theophylline-enoxacin interaction has been studied in six healthy subjects. Theophylline 250 mg was administered p.o., twice daily for 11 days in a sustained release dosage form. On the 4th day of treatment, blood samples were taken every 2 h and urine was collected over 1 dose interval. From Days 5 to 11 coated tablets of enoxacin 400 mg b.i.d. were coadministered. On Day 11 blood and urine were collected as on Day 4. The mean plasma theophylline concentration rose from 4.4 to 15.1 mg/l, corresponding to a 73.6% reduction in total clearance. The urinary excretion of unchanged theophylline increased from 12.7 to 35.3%, whereas the production of metabolites was reduced (1-demethylation 81.4%; 3-demethylation 83.1%, 8-hydroxylation 74.6%). The results indicate that the theophylline-enoxacin interaction may be due to inhibition of the cytochrome P-450 isozymes responsible for theophylline metabolism. Unexpectedly, the renal clearance of theophylline metabolites was found to be drastically reduced when enoxacin was coadministered. This led to unchanged or even to elevated plasma levels of the metabolites. The mechanism of this interaction is still to be elucidated, but it may be due to competition for renal tubular secretion.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-1041
    Keywords: genetic polymorphism ; drug development ; pharmacokinetic variability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Drugs whose principal metabolic pathways are under polymorphic genetic regulation may show considerable interindividual pharmacokinetic variability. This could lead to clinically significant differences in the pharmacological responses of some partients and so might lead the pharmaceutical industry to stop development of the drug. This can be prevented and there are several measures that can be taken to avoid such premature termination of development. They include studies in vitro with human liver samples, and clinical pharmacological experiments designed specifically to examine possible genetic polymorphism in the disposition of the drug.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-1041
    Keywords: ceftizoxime ; cephalosporins ; renal excretion ; tubular reabsorption ; tubular secretion ; healthy volunteers ; biliary excretion ; clearance studies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The kinetics of ceftizoxime, a newly developed cephalosporin, were evaluated in 6 healthy subjects, with respect to its excretory pathways especially by the biliary route. Total, renal and biliary clearance were determined at two different steady states. Steady state was achieved by constant intravenous infusion (604.1 mg/h) over 6 h after an initial loading dose (750 mg); 1.5 h after discontinuation of that infusion, a further infusion was commenced at a lower rate (284 mg/h) over 3 h, the second steady state being reached 0.5 to 1.0 h later. The drug was mainly excreted by the kidneys (56.7 to 92.9% of the dose). Biliary excretion, measured by the duodenal perfusion and marker dilution technique, was low (0.2 to 7.8% of the dose). Urinary and biliary excretion as well as total clearance were not dose-dependent. However, there was pronounced interindividual variation in total (35.2 to 236 ml/min) and renal clearance (10.6 to 208 ml/min), which could both be explained by varying interindividual urinary flow rates (mean flow rate: 0.99 ml/min to 3.14 ml/min). Intraindividual variation in renal clearance was less pronounced, but in the same subject changes in renal clearance were correlated with changes in urinary flow rate. From the varying renal clearance, which exceeded the glomerular filtration rate at high urinary flow rates and was below it at low urinary flow rates, it can be concluded that, in addition to glomerular filtration, tubular secretion and tubular reabsorption are involved in the renal excretion of ceftizoxime. The half-life calculated from two point estimates after discontinuation of the infusion at the higher rate tended to be longer in subjects with high total clearance (e. g. 1.4 h, clearance 223 ml/min) and shorter in subjects with low total clearance (e.g. 0.85 h, clearance 35.2 ml/min). From this it is concluded that the true half-life was not observed after discontinuation of the infusion.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-1041
    Keywords: Serum digoxin ; outpatients ; general practice patients ; patient compliance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Serum digoxin levels were determined in 33 outpatients of a general practice in the countryside, on three occasions at intervals of 8 weeks. All the patients were on long term digoxin treatment, about 2 years on average. About 14 days after the first and the second visits the results of the measurements were sent to the patients, with a comment about their reliability in taking treatment according to the serum digoxin level. At the first visit half of the serum digoxin level were lower than 0.5 ng/ml; the mean serum concentration was 0.52 ng/ml. There was no correlation between serum concentration and age, dose or creatinine level; but there was with replies to the question about regularity of drug intake. The mean serum level at the second and the third visits was 0.88 ng/ml and 0.89 ng/ml, respectively. A correlation was found between the dose and the serum digoxin level. From these results it seems that compliance by the patient plays a major role in producing steady state levels of drugs.
    Type of Medium: Electronic Resource
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