Biomedical subjects

G Stoter

Publications and source records attributed to G Stoter.

At least 55 records · Page 3Linked to original sources

PubMed1999

Femtomole quantitation of 7-ethyl-10-hydroxycamptothecine (SN-38) in plasma samples by reversed-phase high-performance liquid chromatography.

7-Ethyl-10-hydroxycamptothecine (SN-38) is the active metabolite of the topoisomerase I inhibitor and antineoplastic agent, irinotecan (CPT-11). Here, we present a new and sensitive reversed-phase high-performance liquid chromatographic method for the determination of SN-38 in human plasma samples. Sample pretreatment involves a protein precipitation of 1-mL samples with 2 mL of acetonitrile, followed by a one-step solvent extraction with 5 mL of chloroform, with camptothecine used as internal standard. Chromatographic separation was achieved on an analytical column packed with Hypersil ODS material (100 x 4.6 mm i.d., 5 microm P.S.), and isocratic elution with a mixture of acetonitrile:0.1 M ammonium acetate containing 10 mM tetrabutylammonium sulfate (23:77, v/v), pH 5.3 (hydrochloric acid). The column effluent was monitored at excitation and emission wavelengths of 380 and 556 nm, respectively. The limit of quantitation of the method presented was at the low femtomole level ( approximately 8.4 fmol; equivalent to 5 pg/mL), with the standard curves being linear over nearly three orders of magnitude. Intraassay precision was <9%, while interassay variations were between 2 and 5%. The extraction efficiency was concentration independent and averaged 88.0 +/- 14.3% (mean +/- standard deviation; n = 59). The described method will be used in future studies to assess the extent of enterohepatic recirculation of SN-38 in cancer patients following intravenous CPT-11 treatment.

Antineoplastic Agents, Phytogenic↗

PubMed1999

Cremophor EL-mediated alteration of paclitaxel distribution in human blood: clinical pharmacokinetic implications.

We have determined the in vitro and in vivo cellular distribution of the antineoplastic agent paclitaxel (Taxol) in human blood and the influence of Cremophor EL (CrEL), the vehicle used for i.v. drug administration. In the absence of CrEL, the blood:plasma concentration ratio was 1.07+/-0.004 (mean+/-SD). The addition of CrEL at concentrations corresponding to peak plasma levels achieved after the administration of paclitaxel (175 mg/m2 i.v. over a 3-h period; ie., 0.50%) resulted in a significant decrease in the concentration ratio (0.690+/-0.005; P < 0.05). Kinetic experiments revealed that this effect was caused by reduced erythrocyte uptake of paclitaxel by polyoxyethyleneglycerol triricinoleate, the major compound present in CrEL. Using equilibrium dialysis, it was shown that the affinity of paclitaxel for tested matrices was (in decreasing order) CrEL > plasma > human serum albumin, with CrEL present at or above the critical micellar concentration (approximately 0.01%). Our findings in the present study demonstrate a profound alteration of paclitaxel accumulation in erythrocytes caused by a trapping of the compound in CrEL micelles, thereby reducing the free drug fraction available for cellular partitioning. It is proposed that the nonlinearity of paclitaxel plasma disposition in patients reported previously should be reevaluated prospectively by measuring the free drug fractions and whole blood:plasma concentration ratios.

Aged↗

PubMed1999

Determination of doxorubicin and doxorubicinol in plasma of cancer patients by high-performance liquid chromatography.

A high-performance liquid chromatographic assay with fluorescence detection has been developed for the determination of doxorubicin and its metabolite doxorubicinol in plasma of cancer patients. Quantitative extraction was achieved by a single protein-precipitation step of 1-ml samples with 500 microl of acetone in the presence of 100 microl of zinc sulfate [70% (w/v) in water]. Doxorubicin and doxorubicinol were separated isocratically on a column packed with Inertsil ODS-80A material and a mobile phase composed of water:acetonitrile:tetrahydrofuran (76:24:0.5, v/v/v). The related compound daunorubicin was used as internal standard. The column effluent was monitored fluorimetrically at an excitation wavelength of 480 nm and an emission wavelength of 560 nm, with a band width of 40 nm. The calibration graphs of doxorubicin and doxorubicinol were linear over a range of 1.0 to 100 and 0.50 to 50. 0 ng/mL, respectively, with lower limits of quantitation of 1.0 and 0.50 ng/ml. Results obtained from a 4-day validation study demonstrated excellent accuracy (91.0-106%) and precision (0.90-10. 2%) across the calibration ranges for both compounds. The developed method has been applied extensively to a clinical study to examine the pharmacokinetics and metabolism of doxorubicin in patients cotreated with a potent inhibitor of MDR1 P-glycoprotein activity, GF120918.

Antineoplastic Agents↗

PubMed1999

The role of possible risk factors for acute and late renal dysfunction after high-dose interleukin-2, interferon alpha and lymphokine-activated killer cells.

Renal dysfunction is a frequently encountered adverse event following treatment with high-dose interleukin-2 (IL-2). Information about parameters predicting the severity of IL-2-associated renal function abnormalities is limited. In this study the role of possible risk factors in the development of high-dose IL-2-associated acute and long-term renal dysfunction was investigated. A total of 72 patients, who were treated with a regimen consisting of IL-2 (18 MIU m(-2) day(-1) by continuous infusion), interferon alpha (IFNalpha; 5 MIU m(-2) day(-1), intramuscularly) and lymphokine-activated killer (LAK) lymphocytes, were analysed. Serum creatinine measurements were performed daily during treatment, weekly between courses and monthly during follow-up. Pre-and posttreatment 24-h urine samples were collected for calculation of creatinine clearances. Renal dysfunction was observed in 97% of patients. Grade 1 dysfunction (according to WHO criteria) was observed in 20 patients (28%), grade 2 in 37 (51%), grade 3 in 13 (14%) and grade 4 in 0 (0%). Renal dysfunction was reversible in more than 90% of patients. Only 6 patients (8%) suffered a certain amount of permanent function loss. More severe acute renal dysfunction occurred in patients who were experiencing hypertension prior to treatment, those who suffered sepsis during treatment and in men than in women. Sepsis was also associated with irreversible function loss. Other variables such as age, performance status, diabetes mellitus, interval between nephrectomy and start of IL-2 therapy and hypotension during treatment were not important. In conclusion, with high-dose IL-2, renal dysfunction develops in almost every patient and such abnormalities are mostly reversible. Predictors for severe acute renal dysfunction are pre-existing hypertension, sepsis and sex. A septic episode also carries a risk of permanent damage.

Adult↗

PubMed1999

The venotonic drug hydroxyethylrutosiden does not prevent or reduce docetaxel-induced fluid retention: results of a comparative study.

PURPOSE: Fluid retention, which includes peripheral edema, ascites, pleural or pericardial effusion, or a combination of these that is sometimes associated with significant weight gain, is one of the most troublesome cumulative side effects of docetaxel. A suggestive observation from the data base available at the manufacturer (Rhone-Poulenc Rorer) was that patients who received venotonic drugs appeared to tolerate more courses of docetaxel. This prompted a comparative study to investigate whether the venotonic drug hydroxyethylrutosiden could reduce or delay docetaxel-related fluid retention. METHODS: A total of 85 patients with metastatic breast cancer who were treated with docetaxel at a dose of 100 mg/m2 with corticoid comedication were allocated to receive either 300 mg hydroxyethylrutosiden given orally four times daily (group A) or no hydroxyethylrutosiden (group B). The end point for analysis was the development of fluid retention of > or = grade 2. RESULTS: Fluid retention of > or = grade 2 was reported in 14 of 42 patients (33%) in group A and in 15 of 43 patients (35%) in group B and occurred after a median of 4 cycles of docetaxel in both groups. Weight gain was similar in groups A and B. CONCLUSION: We conclude that hydroxyethylrutosiden does not reduce or delay the incidence and severity of docetaxel-related fluid retention.

Adult↗

PubMed1999

Sparse-data set analysis for irinotecan and SN-38 pharmacokinetics in cancer patients co-treated with cisplatin.

The clinical pharmacokinetics of the antineoplastic agent irinotecan (CPT-11) are associated with substantial interpatient variability. The degree to which this variability in CPT-11 exposure impacts upon the response and toxicity of the drug has not yet been properly determined. In general, the area under the plasma concentration-time curve (AUC) is an appropriate indicator of exposure, but requires collection of up to 17 timed blood samples. This presents difficulties if large-scale population samplings are required. The present study involved the development and validation of a strategy to estimate the AUCs of the lactone and total (i.e. lactone plus carboxylate) forms of CPT-11 and its active metabolite SN-38 from a limited number of blood samples in patients co-treated with cisplatin. Using data from 24 patients, univariate and multivariate regression analyses were employed to generate the models. The best predictive models for simultaneous estimation of CPT-11 and SN-38 AUCs were obtained with three time points at 0.5, 1.67 and 5.50 h after start of the 90 min i.v. infusion of CPT-11. The models were tested separately in another group of 24 patients receiving the same combination treatment. This validation set demonstrated that CPT-11 and SN-38 AUCs after standard dose administration could be predicted sufficiently unbiased and precisely with three timed samples to warrant clinical application.

Adult↗

PubMed1999

Phase I and pharmacologic study of the arotinoid Ro 40-8757 in combination with cisplatin and etoposide in patients with non-small cell lung cancer.

This phase I study was performed to assess the feasibility of combining cisplatin/etoposide (VP-16) with the arotinoid Ro 40-8757 and to determine the dose-limiting toxicity (DLT) of Ro 40-8757 in this combination. Patients with non-small cell lung cancer were eligible. Treatment consisted of Ro 40-8757 p.o. day 1-21, cisplatin 100 mg/m2 i.v. on day 2 and VP-16 100 mg/m2 i.v. on day 2-4, repeated every 3 weeks. Eighteen patients were evaluable for toxicity and response. The doses of Ro 40-8757 ranged from 84 mg/m2 once daily to 42 mg/m2 thrice daily (tid). DLT consisting of delayed nausea/vomiting was reached at 42 mg/m2 tid. Consequently, the maximum tolerated dose was set at one dose level below the DLT, i.e. 28 mg/m2 tid. Skin toxicity occurred but was well manageable. Pharmacological analyses showed a small increase in the volume of distribution of cisplatin and VP-16 between the first and third course. However, no relationship with side effects was found. A response was achieved in 50% of patients. The combination of cisplatin/VP-16 with Ro 40-8757 appears to be feasible at a dose schedule of 28 mg/m2 tid. The response rate was at the upper rate of what can be expected with cisplatin and VP-16.

Adult↗

PubMed1999

Phase I and pharmacologic study of BMS-181174 given as a 6 h infusion every 4 weeks to patients with advanced solid tumors.

BMS-181174, a new mitomycin C (MMC) analog, showed more activity than the parent compound in tumor xenografts. In a phase I study with a 5-30 min slow bolus administration, hematologic and vascular toxicity were observed as major side effects. A prolonged infusion was suggested to circumvent the vascular toxicity. In this phase I study BMS-181174 was administered as a 6 h infusion every 4 weeks; the doses studied were 3.2, 6.4, 11.5, 19.0, 32.0, 50.0, 75.0 and 100 mg/m2. Twenty-eight patients were enrolled in the study, the majority with colorectal cancer. Hematologic side effects consisted of thrombocytopenia, and mild leuko- and granulocytopenia. The most distressing non-hematologic side effect was vascular toxicity consisting of phlebosclerosis and phlebitis, becoming dose limiting at 100 mg/m2. One patient developed a hemolytic uremic syndrome at a cumulative dose of 350 mg/m2. Pharmacokinetic data are available for 24 patients. The AUC ranged from 3.35 to 41.49 (microg x h/ml) and was highly correlated with the dose administered (r = 0.83). The kinetics appeared to be linear. One patient with metastatic colon cancer had a partial response of liver metastases. BMS-181174 is a MMC analog with a toxicity profile comparable to that of the parent compound. As doses above 50 mg/m2 are complicated by vascular toxicity precluding multiple administrations, further exploration of BMS-181174 will not be performed.

Adult↗

PubMed1999

Prediction of the systemic exposure to oral 9-amino-20(S)-camptothecin using single-sample analysis.

The purpose of this study was to develop and validate limited-sampling strategies for prediction of the area under the plasma-concentration time curves (AUCs) of the lactone and total (i. e., lactone plus carboxylate) forms of the novel topoisomerase-I inhibitor 9-amino-20(S)-camptothecin (9-AC). Complete pharmacokinetic curves for both drug species were obtained from 32 patients who received the drug orally in a clinical phase I setting at dose levels ranging from 0.25 to 1.10 mg/m2. The concentrations of the lactone and carboxylate forms of 9-AC in plasma were measured by HPLC. Using data from 20 randomly selected patients, forward-stepwise multivariate regression analysis was used to generate modeling strategies incorporating data from one, two, or three plasma samples. The simultaneous optimal prediction of both 9-AC lactone and 9-AC total AUCs was obtained with sample time points at 0.33, 3.0, and 11.0 h after drug dosing. Validation of the models on an independent data set comprising data of the remaining 12 patients demonstrated that 9-AC lactone and 9-AC total AUCs could be predicted sufficiently unbiased and precise using one and two time points: [AUC (ng. h/ml) = 7.103*C3 + 4.333] for 9-AC lactone and [AUC (ng. h/ml) = 9.612*C3 + 13.77*C11 - 44.11] for 9-AC total, where C3 and C11 represent the 9-AC plasma concentrations in ng/ml at 3 and 11 h after drug dosing. Application of the proposed models will be valuable in the determination of 9-AC population pharmacokinetics and permits treatment optimization for patients on the basis of individual pharmacokinetic characteristics through restricted drug monitoring in clinical routines.

Adolescent↗

PubMed1999

Drug-administration sequence does not change pharmacodynamics and kinetics of irinotecan and cisplatin.

In this study, 11 patients with solid tumors were randomized to receive irinotecan (CPT-11; 200 mg/m2) as a 90-min i.v. infusion, immediately followed by cisplatin (CDDP; 80 mg/m2) as a 3-h i.v. infusion in the first course and the reversed sequence in the second course or vice versa. No significant differences in any toxicity were observed between the treatment schedules (decrease in absolute neutrophil count, 74.7 +/- 18.3 versus 80.3 +/- 18.0%; P = 0.41). CPT-11 lactone clearance was similar to single agent data and not significantly different between study courses (60.4 +/- 17.1 versus 65.5 +/- 16.3 liter/h/m2; P = 0.66). The kinetic profiles of the major CPT-11 metabolites SN-38, SN-38 glucuronide, 7-ethyl-10-[4-N-(5-aminopentanoic acid)-1-piperidinolcarbonyloxycamptothecine (APC), and 7-ethyl-10-[4-N-(1-piperidino)-1-amino]carbonyloxycamptothecine (NPC) were also sequence independent (P > or = 0.20). In addition, CPT-11 had no influence on the clearance of nonprotein-bound CDDP (40.8 +/- 16.7 versus 50.3 +/- 18.6 liter/h/m2; P = 0.08) and the platinum DNA-adduct formation in peripheral leukocytes in either sequence (1.94 +/- 2.20 versus 2.42 +/- 1.62 pg Pt/microg DNA; P = 0.41). These data indicate that the toxicity of the combination CPT-11 and CDDP is schedule independent and that there is no mutual pharmacokinetic interaction.

Adult↗

PubMed1999

Disposition of [G-(3)H]paclitaxel and cremophor EL in a patient with severely impaired renal function.

In the present work, we studied the pharmacokinetics and metabolic disposition of [G-(3)H]paclitaxel in a female patient with recurrent ovarian cancer and severe renal impairment (creatinine clearance: approximately 20 ml/min) due to chronic hypertension and prior cisplatin treatment. During six 3-weekly courses of paclitaxel at a dose level of 157.5 mg/m(2) (viz. a 10% dose reduction), the renal function remained stable. Pharmacokinetic evaluation revealed a reproducible and surprisingly high paclitaxel area under the plasma concentration-time curve of 26.0 +/- 1.11 microM.h (mean +/- S.D.; n = 6; c.v. = 4.29%), and a terminal disposition half-life of approximately 29 h. Both parameters are substantially increased ( approximately 1.5-fold) when compared with kinetic data obtained from patients with normal renal function. The cumulative urinary excretion of the parent drug was consistently low and averaged 1.58 +/- 0.417% (+/- S.D.) of the dose. Total fecal excretion (measured in one course) was 52.9% of the delivered radioactivity, and mainly comprised known mono- and dihydroxylated metabolites, with unchanged paclitaxel accounting for only 6.18%. The plasma area under the plasma concentration-time curve of the paclitaxel vehicle Cremophor EL, which can profoundly alter the kinetics of paclitaxel, was 114.9 +/- 5.39 microl.h/ml, and not different from historic data in patients with normal or mild renal dysfunction. Urinary excretion of Cremophor EL was less than 0.1% of the total amount administered. These data indicate that the substantial increase in systemic exposure of the patient to paclitaxel relates to decreased renal metabolism and/or urinary elimination of polar radioactive species, most likely lacking an intact taxane ring fragment.

Aged↗

PubMed1999

Phase I study of subcutaneously administered recombinant human interleukin 12 in patients with advanced renal cell cancer.

A phase I study was conducted to characterize the maximum tolerated dose (MTD), dose-limiting toxicity (DLT), and pharmacokinetics of a single dose followed by three times weekly s.c. injections of recombinant human interleukin 12 (rHuIL-12). The study encompassed 28 patients with advanced renal cell carcinoma. rHuIL-12 was administered on day 1, followed by an observation period of 7 days. Starting on day 8, repeated s.c. injections were administered 3 times a week for 2 weeks. The MTD of the initial injection was evaluated at dose levels of 0.1, 0.5, and 1.0 microg/kg. DLT was observed at 1.0 microg/kg and consisted of fever, perivasculitis of the skin, and leukopenia. The MTD of the subsequent repeated injections after 1 week of rest was studied at dose levels 0.5, 1.0, and 1.25 microg/kg. DLT at 1.25 microg/kg comprised deterioration of performance status, fever, vomiting, mental depression, and leukopenia. Other notable toxicities were oral mucositis and elevation of hepatic enzymes. Fever, leukopenia, and elevation of hepatic enzymes were more severe after the initial injection than after repeated injections at the same dose level. At dose level 0.5 microg/kg, the mean area under the plasma concentration-time curve decreased from 7.4 ng/h/ml after the first injection to 3.3 ng x h/ml (P = 0.034) after repeated administrations, and at dose level 1.0 microg/kg, it ranged from 31.8 ng/h/ml to 6.0 ng x h/ml (P = 0.041). One patient had a partial response and seven had stable disease. The MTD of a single s.c. injection of rHuIL-12 was 0.5 microg/kg, and the MTD of three subsequent administrations per week was 1.0 microg/kg. In comparison with a single administration, the three times weekly administrations at the same dose level was accompanied with a milder pattern of side effects and a reduction of the area under the plasma concentration-time curve.

Adjuvants, Immunologic↗

PubMed1998

Liquid chromatographic determination of irinotecan and three major metabolites in human plasma, urine and feces.

A new simple reversed-phase high-performance liquid chromatographic method was developed for the determination of irinotecan (CPT-11) and three metabolites in human plasma, urine and feces homogenate. The metabolites of interest were 7-ethyl-10-hydroxycamptothecin (SN-38), its beta-glucuronide derivative (SN-38G) and 7-ethyl-10-[4-N-(5-aminopentanoic acid)-1-piperidino]carbonyloxycamptothecin (RPR 121056A; also referred to as APC). Sample pretreatment from the various biological matrices involved a rapid protein precipitation with simultaneous solvent extraction of 250-microl aliquots of sample with 500 microl of methanol-5% (w/v) aqueous perchloric acid (1:1, v/v). Separation of the compounds was achieved on an analytical column packed with Hypersil ODS material (100X4.6 mm I.D., 5 microm), and isocratic elution with a mixture of methanol-0.1 M ammonium acetate containing 10 mM tetrabutylammonium sulphate (30:70, v/v), pH 5.3 (hydrochloric acid). The column effluent was monitored at excitation and emission wavelengths of 355 and 515 nm, respectively. Results from a 4-day validation study indicated that this single-run determination allows for simple, simultaneous and rapid quantitation and identification of all analytes with excellent reliability. The described procedure permits the analysis of patient samples, and will be implemented in future studies to investigate the complete metabolic fate and disposition of CPT-11 in cancer patients.

Camptothecin↗

PubMed1998

Linearized colorimetric assay for cremophor EL: application to pharmacokinetics after 1-hour paclitaxel infusions.

Cremophor EL (CrEL) is a polyoxyethylated castor oil surfactant used in the intravenous formulation of the anticancer drug paclitaxel (Taxol). Quantitative determination of CrEL in patient samples can be achieved by complexation of the compound with the Coomassie brilliant blue G-250 dye in protein-free extracts [Sparreboom, A., Loos, W. J., Verweij, J., De Vos, A. I., Van der Burg, M. E. L., Stoter, G., and Nooter, K., Anal. Biochem. 255, 171-175 (1998)]. A disadvantage of this method of CrEL determination is that the assay plot of absorbance at 595 nm, the peak wavelength of the CrEL-dye complex, versus the concentration of the surfactant is not linear. The present study shows that the nonlinearity is associated with a decrease in the free dye concentration and a reduction in complex formation by increasing the CrEL concentration. By measurement of the ratio of absorbances at the maxima of the red (450 nm) and blue charge forms (595 nm) of Coomassie brilliant blue G-250, a full-scale linear relationship can be obtained over the entire range studied (0.500 to 10.0 microliter/mL). Validation data revealed that transformation of the detection procedure exhibits significantly improved specificity, accuracy(</= 6.33% relative error), and precision (< 10.0%) compared to our previous assay. The modified method was successfully applied to the measurement of CrEL in plasma of 11 cancer patients treated with a 1-h infusion of paclitaxel.

Antineoplastic Agents, Phytogenic↗

PubMed1998

Expression of p53, p21/WAF/CIP, Bcl-2, Bax, Bcl-x, and Bak in radiation-induced apoptosis in testicular germ cell tumor lines.

PURPOSE: Testicular germ cell tumors (TGCTs) represent one of the few tumor types that are curable by antineoplastic therapy, probably due to the high sensitivity of this neoplasm to induction of apoptosis by chemotherapeutic agents and/or ionizing radiation. Here, we tested cell susceptibility to radiation-induced apoptosis in a panel of TGCT cell lines and attempted to correlate this with the known potentially relevant molecular determinants (p53 gene status and Bcl-2 family proteins) of apoptosis. METHODS AND MATERIALS: Induction of apoptosis by gamma-radiation was morphologically recognized in NT2, NCCIT, S2, and 2102 EP using Hoechst/PI staining and additionally confirmed by Western blot analysis of PARP cleavage. The p53 gene status was estimated by sequence analysis. Expression of p21/WAF/CIP was determined by Northern blot analysis and immunoblotting was used to monitor p53, Bax, Bcl-2, Bcl-x, and Bak protein levels. In vitro colony formation was studied to establish clonogenic survival curves. RESULTS: NT2 and NCCIT appeared to be susceptible for radiation-induced apoptosis, contrasting 2102 EP and S2 which were highly resistant. Sequence analysis showed that NT2, S2, and 2102 EP are homozygous for wild-type p53 (wtp53), whereas NCCIT contains mutant p53 (mtp53). NT2 and 2102 EP cells showed radiation-induced p53 upregulation, while NCCIT (mtp53) and S2 (no p53 protein) cells did not. Consistently, gamma-radiation-induced DNA damage resulted in a p53-dependent transactivation of the p21/WAF/CIP gene in NT2 and 2102 EP, but not in mtp53-containing NCCIT cells and p53 nonexpressing S2 cells. Constitutive expression of Bax, Bcl-2, Bcl-x, and Bak was not affected by radiation and showed no correlation with cell susceptibility to radiation-induced apoptosis. A discrepancy was found between apoptosis and reproductive death. CONCLUSIONS: The present study revealed that: i) the presence of wtp53 may not be absolutely required for the hypersensitivity for radiation-induced apoptosis in TGCT cell lines, ii) the molecular mechanism underlying the unique radiosensitivity was independent of the expression of Bcl-2 family proteins, and iii) cell susceptibility to apoptosis induction is not sufficiently informative to predict intrinsic radiosensitivity as determined by clonogenic survival.

Apoptosis↗

PubMed1998

Determination of paclitaxel in human plasma using single solvent extraction prior to isocratic reversed-phase high-performance liquid chromatography with ultraviolet detection.

An isocratic reversed-phase high-performance liquid chromatographic method with ultraviolet detection at 230 nm has been developed for the determination of paclitaxel in human plasma. Plasma samples were prepared by a selective one-step liquid-liquid extraction involving a mixture of acetonitrile-n-butyl chloride (1:4, v/v). Paclitaxel and the internal standard docetaxel were separated using a column packed with ODS-80A material, and a mobile phase consisting of water-methanol-tetrahydrofuran-ammonium hydroxide (37.5:60:2.5:0.1, v/v). The calibration graph for paclitaxel was linear in the range 10-500 ng/ml, with a lower limit of quantitation of 10 ng/ml, using 1 ml plasma samples. The extraction recoveries of spiked paclitaxel and docetaxel to drug-free human plasma were 89.6+/-8.52 and 93.7+/-5.0%, respectively. Validation data showed that the assay for paclitaxel is sensitive, selective, accurate and reproducible. The assay has been used in a single pharmacokinetic experiment in a patient to investigate the applicability of the method in vivo.

Antineoplastic Agents, Phytogenic↗

PubMed1998

Quantitation of Cremophor EL in human plasma samples using a colorimetric dye-binding microassay.

This paper describes an analytical procedure for the quantitative determination of the pharmaceutical vehicle Cremophor EL in human plasma samples. The procedure is based on rapid binding of Coomassie brilliant blue G-250 to Cremophor EL following plasma protein precipitation with acetonitrile and analyte extraction with n-butylchloride. The binding of the dye to Cremophor EL causes a shift in the absorption maximum from 465 to 624 nm, which is monitored using an automated microplate-absorbance reader. The assay permits estimation of Cremophor EL concentrations in the range 0.05-1.00% (v/v) in 50 microL of human plasma, with percentage deviation and precision of < or = 12 and < or = 15%, respectively. The assay was subsequently used to measure Cremophor EL concentrations in plasma samples in support of a project to develop a pharmacokinetic model for this compound in patients receiving paclitaxel.

Antineoplastic Agents, Phytogenic↗

PubMed1998

Synergistic cytotoxicity of cisplatin and topotecan or SN-38 in a panel of eight solid-tumor cell lines in vitro.

The cytotoxicity of cisplatin alone and in combination with topotecan (TPT) or SN-38, two novel topoisomerase I (topo I) inhibitors, was determined in a panel of eight well-characterized human solid-tumor cell lines. Interactions between cisplatin and these topo I inhibitors were investigated using three different administration schedules: (1) simultaneous incubation (C + T and C + S), (2) cisplatin followed by TPT or SN-38 (C --> T and C --> S), and (3) TPT or SN-38 followed by cisplatin (T --> C and S --> C). Median-effect analysis revealed synergistic cytotoxicity in seven of the eight cell lines used. In addition, a significant schedule-dependent synergistic cytotoxicity was found in three of the cell lines used, with C --> T (or C --> S) being the most active schedule. The formation and repair of total cisplatin-DNA adducts in the IGROV-1 ovarian cancer cell line and its cisplatin-resistant subline IGROV(CDDP) was not significantly affected by TPT on simultaneous incubation. In contrast, the number of cisplatin-DNA interstrand cross-links detected in the IGROV-1 and IGROV(CDDP) lines at certain time points was significantly lower after coincubation of the cells with TPT. Assessment of the cell-cycle distribution revealed an accumulation of cells in the G2/M phase after exposure to cisplatin. After exposure to TPT a different pattern was observed that was cell-type-specific and dependent upon the TPT concentration. Although up to 4-fold differences in topo I activity were observed in this panel of cell lines, these differences did not appear to be related to the synergy observed between cisplatin and TPT or SN-38. The observed synergy may at least partly be explained by the increased retention of cisplatin-DNA interstrand cross-links in the presence of topo I inhibitors.

Antineoplastic Combined Chemotherapy Protocols↗