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  • 2000-2004  (11)
  • pharmacokinetics
  • Engineering
Materialart
Erscheinungszeitraum
Jahr
  • 1
    ISSN: 1569-8041
    Schlagwort(e): cisplatin ; pharmacokinetics ; phase I ; oral topotecan
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 1569-8041
    Schlagwort(e): interferon-α ; pharmacokinetics ; renal carcinoma ; retinoids
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Although advanced renal-cell carcinoma (RCC) responds poorly to standardtherapies, phase I–II trials have shown activity for combinations ofinterferon-α2b (IFN) with a retinoid. Alitretinoin (9-cis RA) isan endogenous retinoid with high binding affinity for both RAR and RXRreceptor families. This phase I–II study enrolled 38 patients with RCCin a dose-escalation study of tolerability, pharmacokinetics (PK), andefficacy of twice daily oral 9-cis RA with subcutaneous IFN. Incontrast to studies with similar doses of daily 9-cis RA, PK studiesfound a consistent reduction in 9-cis RA concentrations of about50% after multiple b.i.d. doses of 30 or 50 mg/m2,independent of cotreatment with IFN. In the phase I portion, toxicitiesincluded systemic symptoms typical of IFN and biochemical abnormalitiespreviously associated with retinoids. Two patients experienced dose-limitingtoxicity at 50 mg/m2 b.i.d. of 9-cis RA, thus therecommended phase II dose was 30 mg/m2 b.i.d. One of twenty-sixevaluable patients achieved a durable objective partial remission, andrepeated dosing with this regimen was poorly tolerated. This combination ofretinoid and interferon is not recommended for further study in RCC.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    ISSN: 1569-8041
    Schlagwort(e): BBR3464 ; phase I ; platinum analog ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Objectives:To define the maximum tolerated dose (MTD), thetoxicity and pharmacokinetic profile of BBR3464, a novel triplatinum complex. Patients and methods:Fourteen patients with advanced solid tumorsnot responsive to previous antitumor treatments received BBR 3464 on a daily× 5 schedule every twenty-eighth day. The drug was given as a one-hourinfusion with pre-and post-treatment hydration (500 ml in one hour) and noantiemetic prophylaxis. The starting dose was 0.03 mg/m2/day. Amodified accelerated titration escalation design was used. Total and freeplatinum (Pt) concentrations in plasma and urine were assessed by ICP-MS ondays 1 and 5 of the first cycle. Results:Dose was escalated four times up to 0.17mg/m2/day. Short-lasting neutropenia and diarrhea of late onsetwere dose-limiting and defined the MTD at 0.12 mg/m2. Nausea andvomiting were rare, neither neuro- nor renal toxic effects were observed.BBR3464 showed a rapid distribution phase of 1 hour and a terminal half-lifeof several days. At 0.17 mg/m2 plasma Cmax and AUC on day 5 werehigher than on day 1, indicating drug accumulation. Approximately 10%of the equivalent dose of BBR3464 (2.2%–13.4%) wasrecovered in a 24-hour urine collection. Conclusions:The higher than expected incidence of neutropenia andGI toxicity might be related to the prolonged half-life and accumulation oftotal and free Pt after daily administrations. Lack of nephrotoxicity and thelow urinary excretion support the use of the drug without hydration. Thesingle intermittent schedule has been selected for clinical development.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Veterinary research communications 24 (2000), S. 339-348 
    ISSN: 1573-7446
    Schlagwort(e): anthelmintic ; benzimidazole ; chromatography ; enantiomer ; metabolism ; pharmacokinetics ; sex ; sheep
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Benzimidazole anthelmintic drugs are widely used in veterinary practice. Albendazole sulphoxide (ABZSO) is a benzimidazole drug with two enantiomers, as a consequence of a chiral centre in the sulphoxide group. The kinetics of these enantiomers were studied in male and female sheep. Plasma samples were obtained from the animals between 0.5 and 72 h after oral administration of 7.5 mg/kg of a racemic formulation of ABZSO (total-ABZSO). After a liquid–liquid extraction, the samples were analysed by HPLC to determine the concentrations of total-ABZSO and of the sulphone metabolite (ABZSO2). During the chromatographic analysis, the ABZSO peak was collected and reanalysed by an HPLC technique using a Chiral AGP column to quantify the enantiomeric proportion therein. After kinetic analysis, the AUCs obtained for the (+)-ABZSO were 5.8 and 4.0 times higher than those for the (–)-ABZSO in male and female animals, respectively. The mean residence times were 23.4 and 16.1 h for (+)-ABZSO and 22.2 and 17.4 h for (–)-ABZSO for male and female animals, respectively. The only significant difference between the sexes (p〈0.05) was in the T max of the (–)-ABZSO. Comparing both enantiomers within each sex, significant differences were found in all the kinetic parameters. Finally, no kinetic differences were found between sex for total-ABZSO or ABZSO2.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    ISSN: 1573-904X
    Schlagwort(e): morphine ; nociceptive effect ; electrical stimulation vocalisation method ; microdialysis ; retrodialysis by drug ; pharmacokinetics ; pharmacodynamics ; modelling ; blood-brain barrier transport
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Purpose. To quantify the contribution of distributional processes across the blood-brain barrier (BBB) to the delay in antinociceptive effect of morphine in rats. Methods. Unbound morphine concentrations were monitored in venous blood and in brain extracellular fluid (ECF) using microdialysis (MD) and in arterial blood by regular sampling. Retrodialysis by drug was used for in vivo calibration of the MD probes. Morphine was infused (10 or 40 mg/kg) over 10 min intravenously. Nociception, measured by the electrical stimulation vocalisation method, and blood gas status were determined. Results. The half-life of unbound morphine in striatum was 44 min compared to 30 min in venous and arterial blood (p 〈 0.05). The BBB equilibration of morphine, expressed as the ratio of areas under the curve between striatum and venous blood, was less than unity (0.28 ± 0.09 and 0.22 ± 0.17 for 10 and 40 mg/kg), respectively, indicating active efflux of morphine across the BBB. The concentration-effect relationship exhibited a clear hysterisis with an effect delay half-life of 32 and 5 min based on arterial blood and brain ECF concentrations, respectively. Conclusions. Eighty five percent of the effect delay was caused by morphine transport across the BBB, indicating possible involvement of rate limiting mechanisms at the receptor level or distributional phenomena for the remaining effect delay of 5 min.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Pharmaceutical research 17 (2000), S. 903-905 
    ISSN: 1573-904X
    Schlagwort(e): P-glycoprotein ; hepatic metabolism ; pharmacokinetics ; first-pass metabolism ; drug interaction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 7
    ISSN: 1573-7217
    Schlagwort(e): breast cancer ; 5-fluorouracil ; methotrexate ; pharmacodynamics ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract A novel approach is described to simulate effect site pharmacodynamics of anticancer drugs. This approach is based on (i) the in vivo measurement of unbound, interstitial drug pharmacokinetics (PK) in solid tumor lesions in patients and (ii) a subsequent pharmacodynamic (PD) simulation of the time versus drug concentration profile in an in vitro setting. For this purpose, breast cancer cells (MCF-7) were exposed in vitro to the time versus interstitial tumor concentration profiles of 5-fluorouracil (5-FU) and methotrexate (MTX) from primary breast cancer lesions in patients. This led to a maximal reduction in the viable cell count of 69 on day 4, and of 71 on day 7 for 5-FU and MTX, respectively. This effect was dependent on the initial cell count and was characterized by a high interindividual variability. For 5-FU there was a significant correlation between the maximum antitumor effect and the intratumoral AUC (r = 0.82, p = 0.0005), whereas no correlation could be shown for MTX (r = 0.05, p = 0.88). We conclude, that the in-vivo-PK / in-vitro-PD model presented in this study may provide a rational approach for describing and predicting pharmacodynamics of cytotoxic drugs at the target site. Data derived from this approach support the concept that tumor penetration of 5-FU may be a response-limiting event, while the response to MTX may be determined by events beyond interstitial fluid kinetics.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 8
    ISSN: 1573-7241
    Schlagwort(e): colesevelam hydrochloride ; bile acid sequestrant ; drug interactions ; pharmacokinetics ; digoxin ; warfarin ; quinidine ; verapamil ; metoprolol ; valproic acid
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Colesevelam hydrochloride (colesevelam) is a novel, potent, bile acid–binding agent that has been shown to lower LDL cholesterol a mean of 19% at a dose of 3.8 g/d. We studied the pharmacokinetics of colesevelam coadministered with six drugs: digoxin and warfarin, agents with narrow therapeutic indices; sustained-release verapamil and metoprolol; quinidine, an antiarrhythmic with a narrow therapeutic index; and valproic acid, an antiseizure medication. Six individual studies were single-dose, crossover, with or without a 4.5-g dose of colesevelam. Plasma levels were determined using validated analytical methods. Values for the ratio of ln[AUC(0-t)] with and without colesevelam were 107% for quinidine, 102% for valproic acid, 89% for digoxin, 102% for warfarin, 82% for verapamil, and 112% for metoprolol. Values for the ratio of ln[Cmax] with and without colesevelam were 107% for quinidine, 92% for valproic acid, 96% for digoxin, 99% for warfarin, 69% for verapamil, and 112% for metoprolol. The 90% confidence intervals for these ratios and for values of ln[AUC(0-inf)] that could be determined were within the 80–125% range, with the exception of verapamil. In this study, verapamil had great interindividual variability, with a 28-fold range in Cmax and an 11-fold range in AUC(0-t). In summary, pharmacokinetic studies with colesevelam did not show clinically significant effects on absorption of six other coadministered drugs.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 9
    ISSN: 1573-2568
    Schlagwort(e): azathioprine ; 6-mercaptopurine ; gastrointestinal ; pharmacokinetics ; bioavailability ; inflammatory bowel disease
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Azathioprine (AZA) is used in the treatment of patients with refractory inflammatory bowel disease; however, its use is limited because of systemic toxicity associated with long-term use. Ileocecal delivery of AZA might be advantageous if local intestinal therapeutic effects could be provided with decreased systemic side effects. Decreased cecal systemic absorption would allow higher dosages of AZA to be administered. A two-phase study was performed to compare the systemic exposure of AZA and 6-mercaptopurine (6-MP) following administration of AZA into the stomach, jejunum, and cecum and to compare the systemic exposure to AZA and 6-MP following administration of three different dosages of AZA into the cecum. In phase I, six healthy male volunteers received three 50 mg sequential doses of AZA via an oral tube directly placed into the stomach, jejunum, and cecum, respectively. In phase II, six healthy male volunteers received three different dosages (50, 300, 600 mg of AZA) into the cecum. Plasma concentrations of AZA and 6-MP at various times were quantified and area under the plasma concentration-time curve (AUC) and mean residence time (MRT) were determined. No significant differences in the AUC of AZA were seen at the different sites. The AUC of 6-MP following administration of AZA into the jejunum (67.0 ± 30.1 ng×hr/ml) was higher compared to the stomach (39.9 ± 38.1 ng/hr/ml) and cecum (29.2 ± 10.9 ng×hr/ml). Jejunal absorption was 68% higher than absorption from the stomach and 129% higher than that of the cecum. Gastric absorption was 27% higher than that of the cecum. Increased dosages given into the cecum resulted in increased AUCs of AZA and 6-MP. The AUCs of AZA following 50, 300, and 600 mg dosages were 16.9 ± 7.4, 52.3 ± 67.2, and 132 ± 151 ng×hr/ml, respectively, and the AUCs of 6-MP were 22.2 ± 14.9, 63.4 ± 50.6, and 104 ± 115 ng×hr/ml, respectively. Systemic exposure to 6-MP is reduced following administration of AZA into the cecum, most likely secondary to reduced absorption of 6-MP from the colon. Higher dosages of AZA presented to the cecum do result in increased systemic absorption, but may still allow more drug to be administered with less toxicity than the same dose received orally.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 10
    ISSN: 1573-904X
    Schlagwort(e): amphotericin B ; liposomes ; pharmacokinetics ; toxicokinetics ; tissue distribution ; toxicity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Purpose. Amphotericin B in small, unilamellar liposomes (AmBisome) is safer and produces higher plasma concentrations than other formulations. Because liposomes may increase and prolong tissue exposures, the potential for drug accumulation or delayed toxicity after chronic AmBisome was investigated. Methods. Rats (174/sex) received intravenous AmBisome (1, 4, or 12 mg/kg), dextrose, or empty liposomes for 91 days with a 30-day recovery. Safety (including clinical and microscopic pathology) and toxicokinetics in plasma and tissues were evaluated. Results. Chemical and histopathologic changes demonstrated that the kidneys and liver were the target organs for chronic AmBisome toxicity. Nephrotoxicity was moderate (urean nitrogen [BUN] ≤51 mg/dl; creatinine unchanged). Liposome-related changes (vacuolated macrophages and hypercholesterolemia) were also observed. Although plasma and tissue accumulation was nonlinear and progressive (clearance and volume decreased, half-life increased with dose and time), most toxic changes occurred early, stabilized by the end of dosing, and reversed during recovery. There were no delayed toxicities. Concentrations in liver and spleen greatly exceeded those in plasma; kidney and lung concentrations were similar to those in plasma. Elimination half-lives were 1-4 weeks in all tissues. Conclusions. Despite nonlinear accumulation, AmBisome revealed predictable hepatic and renal toxicities after 91 days, with no new or delayed effects after prolonged treatment at high doses that resulted in plasma levels 〉200 μg/ml and tissue levels 〉3000 μg/g.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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