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  • 1
    ISSN: 1432-0843
    Keywords: Key words Cyclosporine ; Etoposide ; Multidrug resistance ; Pharmacokinetics ; Pharmacodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Purpose: The consequences of using cyclosporine (CsA) therapy to modulate P-glycoprotein-mediated multidrug resistance include increased myelosuppression, hyperbilirubinemia, and altered disposition of the cytotoxin. The purpose of this study was to analyze further the relationship between the degree of leukopenia, and etoposide pharmacokinetic factors. Methods: Each patient initially received intravenously-administered etoposide alone (150–200 mg/m2/d × 3). Later it was given in combination with CsA administered at escalating loading doses (range 2–7 mg/kg) as a 2 hour intravenous (IV) infusion followed by a 3 day continuous infusion, at doses ranging from 5 to 21 mg/kg/day. Serial plasma etoposide concentration-time samples were assayed by high-performance liquid chromatography (HPLC). The area under the curve (AUC) of unbound etoposide was calculated from the total plasma etoposide AUC using a previous published equation [22] where % unbound etoposide = (1.4 × total bilirubin) – (6.8 × serum albumin) + 34.4. The percent decrease in white blood cell (WBC) count and the total or unbound etoposide AUC relationship was fitted to a sigmoid Emax model adapted for paired observations, where: In this equation, Z was the variable describing the two treatment groups (0=no CsA and 1=CsA). The fitted parameters were PDRV50, the pharmacodynamic response variable (PDRV) producing 50% of the maximal response; parameter β, which describes the effect of the treatment group on the PDRV50; parameter H (Hill constant), which defines the slope of the response curve and parameter δ, which describes the effect of the treatment group on parameter H. Results: CsA at a median concentration of 1,938 μg/ml resulted in a median increase in the total plasma etoposide AUC by 103% and the calculated unbound plasma etoposide AUC by 104%. This paralleled a 12% greater median percent decrease in WBC count during etoposide + CsA treatment (72% vs. 84%, P=0.03). The percent decrease in WBC count and total or unbound etoposide AUC relationship was fitted to the sigmoid Emax model. The model using the unbound etoposide AUC described the data adequately (r=0.790) and was precise, with a mean absolute error of 6.4% (95% confidence interval: −4.9, 7.8). The fitted parameter-estimates suggested that at equivalent unbound etoposide AUC values above 10 μg × h/ml, the sigmoid Emax model predicted a 5% greater WBC count suppression when CsA was added to the treatment regimen. Conclusion: These findings suggest that a small degree of the enhanced myelosuppression observed with CsA combined with etoposide might be attributable to inhibition of P-glycoprotein in bone marrow precursor cells. However, the majority of the effect observed appears to be due to pharmacokinetic interactions, which result in increases in unbound etoposide.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 620 (1994), S. 457-466 
    ISSN: 0044-2313
    Keywords: Organomolybdenum-bismuth halide complexes ; preparation ; crystal structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Untersuchungen zur Synthese und Struktur von Organomolybdän-Bismuthalogenid-KomplexenDie Reaktionen von BiBr2Ph mit Na/K[Mo(CO)3(η—C5H5)], von [BiPh{Mo(CO)3(η—C5H5)}2] mit BiBr2Ph oder BiBr3 und BiPh3 mit [Bi{Mo(CO)3(η—C5H5)}3] ergeben den Komplex [BiBrPh{Mo(CO)3(η—C5H5)}] 1, der röntgenographisch charakterisiert worden ist. Der Komplex 1 besteht aus einem Bismutzentrum mit einem Bromatom, einer Phenylgruppe und einer Mo(CO)3(η—C5H5)-Einheit. Eine intermolekulare Wechselwirkung besteht zum Bromatom eines benachbarten Moleküls, wodurch sich eine eindimensionale polymere Struktur ergibt. Bei der Umsetzung mit einer Bromidabgebenden Verbindung wird zunächst der anionische Komplex [BiBr2Ph{Mo(CO)3(η—C5H5)}2]- 3- und bei längerer Reaktion [BiBr2{Mo(CO)3(η—C5H5)}2]- 5- gebildet, das als [Ph4P]+-Salz röntgenographisch charakterisiert wurde. Der Komplex 5-, der am Bi zwei Br und zwei Mo(CO)3(η—C5H5)-Einheiten enthält, liegt in einer Struktur zwischen unvollständig trigonal-pyramidal und tetraedrisch vor. Der Komplex [PPN]2[Bi2Cl6{Mo(CO)3(η—C5H5)}2] 8 wurde ebenfalls dargestellt und röntgenographisch charakterisiert. Es liegt ein dimeres Anion vor, das aus zwei quadratischen Pyramiden mit einer gemeinsamen Kante besteht, in denen die Chloratome in der Basisebene und die zwei Mo(CO)3(η—C5H5)-Einheiten sich an den Spitzen in gegenüberliegenden Positionen befinden.
    Notes: The reactions between either BiBr2Ph and Na/K[Mo(CO)3(η—C5H5)], [BiPh{Mo(CO)3(η—C5H5)}2] and BiBr2Ph, or BiBr3 and BiPh3 and [Bi{Mo(CO)3(η—C5H5)}3] afford the complex [BiBrPh{Mo(CO)3(η—C5H5)}] 1 which has been characterised by X-ray crystallography. Complex 1 comprises a bismuth centre bonded to a bromine atom, a phenyl group and a Mo(CO)3(η—C5H5) fragment together with a longer secondary intermolecular interaction between a bromine from an adjacent molecule which results in a one-dimensional polymeric structure. Addition of a source of bromide anion to 1 affords the anionic complex [BiBr2Ph{Mo(CO)3(η—C5H5)}]- 3- although prolonged reaction results in the complex [BiBr2{Mo(CO)3(η—C5H5)}2]- 5- which was characterised by X-ray crystallography as its [Ph4P]+ salt. Complex 5- comprises a mononuclear bismuth centre bonded to two bromine atoms and two Mo(CO)3(η—C5H5) fragments in a geometry which lies between equatorially vacant trigonal bipyramidal and tetrahedral. The complex [PPN]2[Bi2Cl6{Mo(CO)3(η—C5H5)}2] 8 has also been synthesised and characterised by X-ray crystallography. A dimeric dianion is observed which can be viewed as two edge-shared square-based pyramids with chlorine atoms in the basal planes and Mo(CO)3(η—C5H5) fragments in the apical positions on opposite sides of the Bi2Cl6 plane.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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