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  • 1
    ISSN: 1432-0843
    Keywords: Key words S9788 ; Doxorubicin ; Pharmacokinetics ; Multidrug resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Purpose: The objectives of this phase I study were to evaluate the toxic effects and the maximum tolerated dose (MTD) of S9788, a new modifier of multidrug resistance (MDR), when given alone and in combination with doxorubicin to patients with advanced solid tumors; to achieve a potentially active plasma concentration of S9788; and to study the pharmacokinetics of both drugs. Methods: A total of 26 patients (median age 58 years) entered the study. S9788 was given alone as a 30-min infusion at day 1 and in combination with a 50-mg/m2 bolus of doxorubicin at days 8 and 29. Dose levels of S9788 were escalated from 8 to 96 mg/m2 according to the modified Fibonacci scheme. Plasma samples were taken predose as well as during and up to 48 h after the beginning of infusion for S9788 and doxorubicin quantitation. Fractionated urine samples were also collected for up to 24 h for S9788 determination. Results: The dose-limiting side effects of S9788 consisted of bradycardia, sometimes associated with faintness or dizziness. The MTD of S9788 was 96 mg/m2. No enhancement of doxorubicin toxicity was observed. One partial response (duration 140 days) was observed at 96 mg/m2 in a patient with multiple lung metastases from a refractory urothelial carcinoma. Pharmacokinetic studies were performed in 24 patients. Since the mean apparent elimination half-life of S9788 was 46 ± 23 h and the last plasma sampling time was 48 h, only model-independent parameters were considered. Plasma levels of S9788 were below the limit of quantitation (4 × 10–3μM ) before each drug administration. S9788 plasma levels of up to 3.7 μM could be obtained with this administration schedule. The urinary elimination of the unchanged drug was negligible, whatever the collection period. In spite of the large inter- and intraindividual variability, plasma pharmacokinetics of S9788 given as a 30-min i.v. infusion were linear up to 96 mg/m2 and were not modified by doxorubicin administration. Doxorubicin pharmacokinetic parameters did not seem to be influenced by S9788 coadministration. Conclusion: The dose-limiting toxicity of S9788 consisted of bradycardia or clinical symptoms suggesting a vasovagal impact such as faintness or dizziness. The MTD of S9788 was 96 mg/m2. The pharmacokinetic parameters of doxorubicin in this study were close to those usually described and were not influenced by escalation of the S9788 dose. No pharmacokinetic interaction was observed between S9788 and doxorubicin. The clinical tolerability of the combined treatment is in good agreement with the pharmacokinetic findings, since no enhancement of doxorubicin toxicity was observed.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0843
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Previous pharmacokinetic studies of i.v. highdose melphalan (HDM) have demonstrated large interindividual variations in the pharmacokinetic parameters. We therefore studied the possibility of using a test dose of the drug to determine the level of a subsequent therapeutic dose. This study was undertaken to establish whether the pharmacokinetics of melphalan were linear and reproducible within the same patient and determine whether a linear extrapolation could be carried out from the test dose. The first eight patients were studied on two occasions separated by 2 hours (repeatability stage). Although reasonable evidence for linear pharmacokinetics was obtained from these patients, the data suggested a number of factors that might have introduced errors. Therefore, the second group of ten patients were treated on a slightly different protocol on two occasions 24 h apart (linearity stage). The ratios of the two doses ranged from 1 to 8 (repeatability stage) and from 2.6 to 10 (linearity stage). During both stages there was a good correlation between the AUC measured for the second infusion and that predicted from the first (r=0.929 and r=0.943, respectively). We conclude that a test dose can be used to determine the subsequent dose of melphalan necessary to produce a desired AUC.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0843
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The pharmacokinetic parameters of the alkylating agent melphalan were determined in 15 children and 11 adults with advanced malignant solid tumors. High IV bolus doses of 140 mg/m2 were given under standard hyperhydration conditions and followed by autologous bone marrow grafting. In all cases the time-concentration curves could be best fitted to a biexponential pattern. A high scattering of drug concentrations was observed in our patients, the disposition half-lives ranging in the whole group from 17.8 to 71.2 min. The areas under the curves also showed a wide variation, ranging from 175 to 682 mg l-1 min-1. In all patients, melphalan levels in plasma were unmeasurable at 8 h or earlier, indicating that bone marrow can be safely reinfused at that time. No difference was apparent between children and adults regarding the drug pharmacokinetics. In each of 11 cerebrospinal fluid samples drawn 45–150 min after melphalan administration, drug levels were unmeasurable.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-0843
    Keywords: Key wordsEtoposide ; Population pharmacokinetics ; Unbound fraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A population pharmacokinetics study using the NONMEM program was undertaken to determine the effects of different covariates on the pharmacokinetic parameters of etoposide. A total of 1,044 plasma etoposide concentrations were determined by high-performance liquid chromatography (HPLC) in 100 patients (pts; 75 men and 25 women aged 25–85 years) treated for various tumor types with i.v. (57 pts) or oral (43 pts) etoposide. For 67 pts, etoposide plasma protein binding was determined by equilibrium dialysis; the unbound fraction ranged from 4% to 24%. A linear two-compartment model with first-order absorption (for oral dosing) accurately described the concentration versus time data. The central and peripheral volumes of distribution were significantly correlated with the body surface area [Vc (L) = 5.5 × BSA (m2) and Vp = 4.1 × BSA], but even after BSA had been taken into account, the interindividual variability of the two volumes remained high (34% and 57%, respectively). The clearance (CL) was not correlated with the following covariates: age, BSA, sex, height, and levels of serum bilirubin and liver enzymes. The final regression model for CL was CL (ml/min) = 49.8 × (1 − 0.009 × PRO) × WT/Scr + 33.8 × (1 − 0.29 × META) × (1− (1 − 0.012 × ALB), where ALB , PRO , WT ,and Scr, respectively, were albuminemia, proteinemia (g/l), weight (kg), and serum creatinine (μM ) and META = 1 if the patient had liver metastases (otherwise, META = 0). The interindividual variability in CL (mean value 30 ml/min) decreased only from 32% to 26% when these covariates were taken into account. The mean oral bioavailability was 66%, showing an interindividual variability of 37%. The plasma clearance of the unbound fraction was strongly and negatively correlated with Scr but was not dependent on either PRO or ALB. These data show that modifications in PRO levels do not directly affect plasma exposure to unbound etoposide. This analysis makes possible the rational consideration of modifications of covariates such as Scr in etoposide dosing. This population data base will constitute the prerequisite for adaptative control with feedback dosing for continuous oral administration of etoposide.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-0843
    Keywords: Key words Bayesian estimation ; Pharmacokinetics ; Etoposide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Etoposide (VP16), a widely used anticancer drug, is a topoisomerase II inhibitor. A number of studies have highlighted a correlation between hematologic toxicity and pharmacokinetic or physiological parameters. Other studies have also suggested that the anti-tumor response could be related to the plasma etoposide concentration. Therefore, it would seem of interest to individualize VP16 dose regimens on the basis of pharmacokinetic parameters. The aim of this study was to develop and validate a limited-sampling strategy allowing VP16 pharmacokinetic evaluation with minimal disturbance to the patient. A total of 34 patients (54 kinetics) received VP16 at various dose regimens, with doses ranging between 30 and 200 mg and infusion times varying between 0.5 and 2 h. The statistical characteristics of the pharmacokinetic parameters were assessed from the first courses of treatment performed in 23/34 patients; then the following three-sample protocol was designed: the end of the infusion and 5 and 24 h after the start of the infusion. For validation of the model the main pharmacokinetic parameters (clearance, half-lives, volume of distribution) were estimated in the 11 remaining patients by maximum-likelihood estimation (ML) and by Bayesian estimation (BE) using the three sampling times designed. Statistical comparison showed a good concordance between ML and BE estimates (the bias for clearance was –1.72%). The limited-sampling strategy presented herein can thus be used for accurate estimation of VP16 pharmacokinetic parameters.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-0646
    Keywords: docetaxel ; plasma assay ; clinical trials ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract We have developed a specific and sensitive method aiming atdocetaxel (Taxotere®) determination in plasma of treatedpatients. This involved solid-phase extraction of 1 ml of plasmaonto carboxylic acid (CBA) grafted silica cartridges followed byreversed-phase liquid chromatography with UV detection. The bestselectivity was obtained through the use of C18 Uptisphere® asstationary phase. The low limit of quantitation obtained (LOQ:5 ng/ml) allowed measurements of docetaxel up to 24 hours afterone-hour infusions with low dosages of drug (60 mg/m2). Themethod was applied successfully to monitor docetaxel plasma levelswithin two protocols associating fixed dosages of either methotrexate or gemcitabine with escalating doses of Taxotere®.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-0646
    Keywords: KW-2149 ; mitomycin C analog ; phase I ; pulmonary toxicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary KW-2149 is a new mitomycin C (MMC) analog, forming DNA-DNA and DNA-protein crosslinking 20-fold more effectively than MMC. Because of its equal or superiorin vitro andin vivo activity compared to MMC, a phase I study was initiated with an intravenous bolus injection every three weeks. This study was interrupted after dose escalation from 5 mg/m2 to 100 mg/m2 because of subacute and dose dependent pulmonary toxicity. Because of the lack of other end-organ toxicity, the moderate hematological toxicity and the observed antitumor effect, a second phase I study was initiated with a 24 hour continuous infusion. The starting dose was 50 mg/m2 and further escalation depended on observed pulmonary toxicity. Four patients were entered into this study and they received in total 17 courses. Toxicity was again mainly restricted to the lungs with one patient suffering grade 2 dyspnoe and another one grade 1 dyspnoe. Three patients had a substantial change in the carbon monoxide (CO) diffusion capacity. Pharmacokinetic data from these patients showed very low plasma levels both for KW-2149, as for both known metabolites M-16 and M-18. This study demonstrates that pulmonary toxicity continues to occur with KW-2149, in spite of the assurance of low plasma levels of both the parent compound and the known metabolites. The interesting activity of this compound has stimulated further in-depth research towards mechanisms of pulmonary toxicity and means of preventing them.
    Type of Medium: Electronic Resource
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