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  • 1
    Electronic Resource
    Electronic Resource
    Effect of Amiodarone and Desethylamiodarone on the Pharmacokinetics of Antipyrine in the Rat (1987)
    Springer
    Pharmaceutical research 4 (1987), S. 251-254 
    Details
    ISSN: 1573-904X
    Keywords: amiodarone ; antipyrine ; desethylamiodarone ; drug metabolism ; drug interactions ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The effect of amiodarone on hepatic drug metabolism in vivo was examined in the rat using antipyrine as a model substrate. Pretreatment with oral amiodarone hydrochloride, 100 mg/kg/day, for 5 days resulted in a 19% reduction in antipyrine clearance and a 22% increase in half-life. The administration of single oral doses of amiodarone hydrochloride, 100 mg/kg, 1 or 5 hr prior to antipyrine administration had no significant effect on antipyrine pharmacokinetics. The administration of a single intravenous dose of amiodarone hydrochloride, 50 mg/kg, reduced antipyrine clearance by 32% and increased the half-life by 46%. The desethyl metabolite of amiodarone was also found to reduce antipyrine clearance (21%) after a single oral dose of 100 mg/kg.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1016468430618
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Dextromethorphan Pretreatment Induces Antipyrine Clearance in the Rat (1988)
    Springer
    Pharmaceutical research 5 (1988), S. 437-439 
    Details
    ISSN: 1573-904X
    Keywords: antipyrine ; dextromethorphan ; drug metabolism ; enzyme induction ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Numerous agents that undergo extensive first-pass metabolism have been shown to inhibit oxidative drug metabolism. To examine whether this effect is related to the chemical structure or pharmacokinetic characteristics of the inhibiting agent, we determined the effect of dextromethorphan (a compound which exhibits pharmacokinetic similarities to, but is chemically dissimilar from, previously studied agents) on the disposition of antipyrine. A single oral dose of dextromethorphan hydrobromide, 100 mg/kg, 1 hr prior to antipyrine administration had no significant effect on the pharmacokinetics of this model substrate. The administration of dextromethorphan at the same dose twice daily for 3 days and an additional dose 1 hr prior to antipyrine administration resulted in a 33% increase in the clearance of antipyrine. These data indicate that dextromethorphan is capable of inducing hepatic microsomal enzymes. Studies are needed to determine if this effect also occurs upon chronic administration in humans. These data suggest that the pharmacokinetic characteristic of extensive first-pass metabolism is not necessarily associated with inhibition of drug metabolism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015940518439
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of Hydralazine on the Elimination of Antipyrine in the Rat (1987)
    Springer
    Pharmaceutical research 4 (1987), S. 515-518 
    Details
    ISSN: 1573-904X
    Keywords: antipyrine ; drug metabolism ; hydralazine ; hypothermia ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The concomitant administration of hydralazine with metoprolol or propranolol substantially increases the oral bioavailability of these beta-blockers, presumably via reduction of the first-pass effect. It has been suggested that this effect may be secondary to a decrease in the intrinsic clearance of propranolol, possibly by inhibition of oxidative metabolism. To examine the possibility that hydralazine alters oxidative metabolism in vivo, the effect of hydralazine on the pharmacokinetics of antipyrine was examined in the rat. The oral administration of hydralazine hydrochloride, 7.5 mg/kg, 15 min prior to antipyrine administration reduced antipyrine clearance from 9.66 ± 1.18 to 8.19 ± 0.76 ml/min/kg (P 〈 0.05). Hydralazine was observed to cause substantial hypothermia. The study was repeated in temperature-regulated animals and no alteration in antipyrine clearance was found. Two doses of hydralazine in temperature-regulated rats also failed to alter antipyrine clearance. Thus, it appears that the effect of hydralazine on antipyrine clearance is secondary to the hypothermic effect of hydralazine and not due to a direct inhibition of cytochrome P-450-mediated enzyme activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1016487824200
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Raman shifts due to variations in backbone planarity in a group of polydiacetylenes (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 109-112 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polydiacetylene xBCMU and 9PA crystals, solutions and solution-cast films vary in colour due to differences in backbone order and planarity. Associated with the colour changes are increases in the Raman frequencies of the triple and double backbone bond vibrational modes from those values found in the highly ordered single crystals. These increases are strongly correlated and the ratio of the change in the frequency of the triple bond mode to that of the double bond mode is found to be 1.6 (±0.1) over a wide variation in order. This ratio is compared with the values of 0.3 found under uniform strain and 1.1 predicted by a model of acetylenic to butatrienic delocalisation. The relationship between the Raman frequencies of the yellow solutions and melts and those of the crystal phases suggests that in the former the backbone has a continuous and smoothly curving ‘worm-like’ conformation. Models involving the break-up of the conjugated system by large-angle bond rotations appear to be incorrect for polydiacetylenes. These results have important consequences for theoretical models that predict the dependence of electron delocalisation on backbone order and planarity in polydiacetylenes.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
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