Comprehensive pharmaceutical care to prevent drug-related readmissions of dependent-living elderly patients: a randomized controlled trial

BACKGROUND

Elderly patients are vulnerable to adverse drug reactions (ADRs). Drug-related readmissions (DRRs) can be a major consequence of ADR. Therefore, this study aimed to investigate the effects of a ward-based, comprehensive pharmaceutical care service on the occurrence of DRRs as the endpoint in dependent-living elderly patients.

METHODS

A randomized, controlled trial was performed at a German University Hospital. Patients fulfilling the following criteria were eligible: admission to a cooperating ward, existing drug therapy at admission, 65 years of age and older, home-care or nursing home residents in ambulatory care, and a minimum hospital stay of three days. Patients received either standard care (control group) or pharmaceutical care (intervention group). Follow-up consultations were conducted for each patient at 1, 8, 26, and 52 weeks after discharge. The time to DRR was defined as the primary outcome measure and was analysed using the log-rank test. The Cox-proportional hazard model was used for risk factor analysis.

RESULTS

Sixty patients (n = 31 intervention group, n = 29 control group) participated in the study. For patients in the intervention group, the median time to DRR was prolonged; however, the level of statistical significance was not reached (log-rank test P = 0.068; HR = 3.28, P = 0.086). When the risk factors 'age' or 'length of stay on the ward' were added to the Cox proportional hazard model, patients in the control group exhibited a significantly higher risk of experiencing a DRR than patients of the intervention group (HR = 4.62; P = 0.028 including age and HR = 5.76; P = 0.033 including length of stay on the ward).

CONCLUSIONS

Our findings demonstrate the successful implementation of ward-based, comprehensive pharmaceutical care for dependent-living elderly. Despite a low participation rate, which led to an underpowered study, the results provide a preliminary efficacy signal and effect size estimates to power a definitive trial.

TRIAL REGISTRATION

Clinicaltrials.gov identifier: NCT01578525 , prospectively registered April 13, 2012.

Population Modeling Integrating Pharmacokinetics, Pharmacodynamics, Pharmacogenetics, and Clinical Outcome in Patients With Sunitinib-Treated Cancer

The tyrosine kinase inhibitor sunitinib is used as first‐line therapy in patients with metastasized renal cell carcinoma (mRCC), given in fixed‐dose regimens despite its high variability in pharmacokinetics (PKs). Interindividual variability of drug exposure may be responsible for differences in response. Therefore, dosing strategies based on pharmacokinetic/pharmacodynamic (PK/PD) models may be useful to optimize treatment. Plasma concentrations of sunitinib, its active metabolite SU12662, and the soluble vascular endothelial growth factor receptors sVEGFR‐2 and sVEGFR‐3, were measured in 26 patients with mRCC within the EuroTARGET project and 21 patients with metastasized colorectal cancer (mCRC) from the C‐II‐005 study. Based on these observations, PK/PD models with potential influence of genetic predictors were developed and linked to time‐to‐event (TTE) models. Baseline sVEGFR‐2 levels were associated with clinical outcome in patients with mRCC, whereas active drug PKs seemed to be more predictive in patients with mCRC. The models provide the basis of PK/PD‐guided strategies for the individualization of anti‐angiogenic therapies.

Validation of the German patient-reported outcomes version of the common terminology criteria for adverse events (PRO-CTCAE™)

BACKGROUND

Integrating the patient's perspective has become an increasingly important component of adverse event reporting. The National Cancer Institute has developed a Patient-Reported Outcomes version of the Common Terminology Criteria for Adverse Events (PRO-CTCAE™). This instrument has been translated into German and linguistically validated; however, its quantitative measurement properties have not been evaluated.

PATIENTS AND METHODS

A German language survey that included 31 PRO-CTCAE items, as well as the EORTC QLQ-C30 and the Oral Mucositis Daily Questionnaire (OMDQ), was distributed at 10 cancer treatment settings in Germany and Austria. Item quality was assessed by analysis of acceptability and comprehensibility. Reliability was evaluated by using Cronbach's' alpha and validity by principal components analysis (PCA), multitrait-multimethod matrix (MTMM) and known groups validity techniques.

RESULTS

Of 660 surveys distributed to the study centres, 271 were returned (return rate 41%), and data from 262 were available for analysis. Participants' median age was 59.7 years, and 69.5% of the patients were female. Analysis of item quality supported the comprehensibility of the 31 PRO-CTCAE items. Reliability was very good; Cronbach's' alpha correlation coefficients were >0.9 for almost all item clusters. Construct validity of the PRO-CTCAE core item set was shown by identifying 10 conceptually meaningful item clusters via PCA. Moreover, construct validity was confirmed by the MTMM: monotrait-heteromethod comparison showed 100% high correlation, whereas heterotrait-monomethod comparison indicated 0% high correlation. Known groups validity was supported; PRO-CTCAE scores were significantly lower for those with impaired versus preserved health-related quality of life.

CONCLUSION

A set of 31 items drawn from the German PRO-CTCAE item library demonstrated favourable measurement properties. These findings add to the body of evidence that PRO-CTCAE provides a rigorous method to capture patient self-reports of symptomatic toxicity for use in cancer clinical trials.

Open-label, randomized study of individualized, pharmacokinetically (PK)-guided dosing of paclitaxel combined with carboplatin or cisplatin in patients with advanced non-small-cell lung cancer (NSCLC)

BACKGROUND

Variable chemotherapy exposure may cause toxicity or lack of efficacy. This study was initiated to validate pharmacokinetically (PK)-guided paclitaxel dosing in patients with advanced non-small-cell lung cancer (NSCLC) to avoid supra- or subtherapeutic exposure.

PATIENTS AND METHODS

Patients with newly diagnosed, advanced NSCLC were randomly assigned to receive up to 6 cycles of 3-weekly carboplatin AUC 6 or cisplatin 80 mg/m(2) either with standard paclitaxel at 200 mg/m(2) (arm A) or PK-guided dosing of paclitaxel (arm B). In arm B, initial paclitaxel dose was adjusted to body surface area, age, sex, and subsequent doses were guided by neutropenia and previous-cycle paclitaxel exposure [time above a plasma concentration of 0.05 µM (Tc>0.05)] determined from a single blood sample on day 2. The primary end point was grade 4 neutropenia; secondary end points included neuropathy, radiological response, progression-free survival (PFS) and overall survival (OS).

RESULTS

Among 365 patients randomly assigned, grade 4 neutropenia was similar in both arms (19% versus 16%; P = 0.10). Neuropathy grade ≥2 (38% versus 23%, P < 0.001) and grade ≥3 (9% versus 2%, P < 0.001) was significantly lower in arm B, independent of the platinum drug used. The median final paclitaxel dose was significantly lower in arm B (199 versus 150 mg/m(2), P < 0.001). Response rate was similar in arms A and B (31% versus 27%, P = 0.405), as was adjusted median PFS [5.5 versus 4.9 months, hazard ratio (HR) 1.16, 95% confidence interval (CI) 0.91-1.49, P = 0.228] and OS (10.1 versus 9.5 months, HR 1.05, 95% CI 0.81-1.37, P = 0.682).

CONCLUSION

PK-guided dosing of paclitaxel does not improve severe neutropenia, but reduces paclitaxel-associated neuropathy and thereby improves the benefit-risk profile in patients with advanced NSCLC.

CLINICAL TRIAL INFORMATION

NCT01326767 (https://clinicaltrials.gov/ct2/show/NCT01326767).

Defining the role of MRP-mediated efflux and glutathione in detoxification of oxaliplatin

Albeit platinum complexes are widely used in cancer chemotherapy, their cellular processing has not been completely elucidated so far. In this study the effects of modulating multidrug resistance-associated protein (MRP)-mediated efflux and glutathione (GSH) depletion on the cytotoxicity of oxaliplatin were assessed in a human ileocecal colorectal adenocarcinoma cell line and its oxaliplatin-resistant variant. Upon oxaliplatin exposure, DNA platination was elevated by co-incubation with Gü83, a MRP1 and MRP2 inhibitor, but cytotoxicity was not increased. Addition of oxaliplatin did not alter the cellular GSH content. Following GSH depletion, platinum accumulation was unchanged but cytotoxicity was increased in oxaliplatin-sensitive cells. In conclusion, modulation of MRP-mediated efflux did not affect oxaliplatin cytotoxicity in the investigated cell lines. Intracellular GSH depletion seems to sensitize the cells but does not overcome resistance.

Pharmacokinetic/pharmacodynamic modeling of biomarker response to sunitinib in healthy volunteers

A pharmacokinetic/pharmacodynamic (PK/PD) study of the tyrosine kinase inhibitor sunitinib was conducted in 12 healthy volunteers using blood pressure and circulating biomarker levels as PD markers. Blood pressure was measured, and plasma concentration-time courses of sunitinib, its major metabolite SU12662, vascular endothelial growth factors VEGF-A and VEGF-C, and soluble VEGF receptor-2 (sVEGFR-2) were studied in healthy subjects receiving 50 mg of sunitinib orally for 3-5 consecutive days. Using NONMEM, PK/PD models were established that predicted changes (expressed as multiples relative to baseline values) in systolic blood pressure, diastolic blood pressure, VEGF-A level, and sVEGFR-2 level, of 1.10, 1.18, 2.24, and 0.76, respectively, for a typical subject after 4 weeks of treatment with 50 mg/day. Simulated blood pressure-time courses compare excellently with published data in patients, whereas changes in circulating biomarkers were greater in patients than simulations suggest for healthy subjects. In conclusion, the tumor-independent pharmacological response to sunitinib could be described by PK/PD models, thereby facilitating model-based investigations with antiangiogenic drugs, using blood pressure and circulating proteins as biomarkers.

Oxaliplatin-DNA adduct formation in white blood cells of cancer patients

In this study, we investigated the kinetics of oxaliplatin-DNA adduct formation in white blood cells of cancer patients in relation to efficacy as well as oxaliplatin-associated neurotoxicity. Thirty-seven patients with various solid tumours received 130 mg m(-2) oxaliplatin as a 2-h infusion. Oxaliplatin-DNA adduct levels were measured in the first cycle using adsorptive stripping voltammetry. Platinum concentrations were measured in ultrafiltrate and plasma using a validated flameless atomic absorption spectrometry method. DNA adduct levels showed a characteristic time course, but were not correlated to platinum pharmacokinetics and varied considerably among individuals. In patients showing tumour response, adduct levels after 24 and 48 h were significantly higher than in nonresponders. Oxaliplatin-induced neurotoxicity was more pronounced but was not significantly different in patients with high adduct levels. The potential of oxaliplatin-DNA adduct measurements as pharmacodynamic end point should be further investigated in future trials.

Marked elevation in homocysteine and homocysteine sulfinic acid in the cerebrospinal fluid of lymphoma patients receiving intensive treatment with methotrexate

OBJECTIVE

Interference of methotrexate (MTX) with the metabolism of homocysteine may contribute to MTX neurotoxicity. In this pilot study we measured the concentration of homocysteine and related metabolites in the cerebrospinal fluid (CSF) of patients with primary central nervous system lymphoma undergoing intensive treatment with MTX.

MATERIAL AND METHODS

CSF samples from lymphoma patients (n = 4) were drawn at the end of high-dose MTX infusions (3-5 g/m2/24 h, HDMTX) and one day after intraventricular injections of MTX (3 mg, ICVMTX) or cytarabine (30 mg) and analyzed for homocysteine, cysteine, sulfur-containing excitatory amino acids (cysteine sulfinic acid, cysteic acid, homocysteine sulfinic acid and homocysteic acid), S-adenosylmethionine, 5-methyltetrahydrofolate and MTX. The concentration of homocysteine, cysteine and sulfur-containing excitatory amino acids were also measured in the CSF of a reference population not exposed to MTX. The Wilcoxon signed rank-test and the Friedman test were used to compare concentrations of homocysteine and its metabolites at various time-points during chemotherapy. Comparison of patient and control samples were performed using the Mann-Whitney U-test. Allelic variants of homocysteine metabolism previously shown to influence MTX neurotoxicity (MTHFR c.677C>T, MS c.2756A>G and Tc2 c.776C>G) were also analyzed.

RESULTS

After application of HD- and ICVMTX, the CSF homocysteine concentrations in the lymphoma patients were markedly elevated and significantly higher than those in the control group (p < 0.05, Mann-Whitney U-test), whereas 5-methyltetrahydrofolate was depleted. A rapid elevation of homocysteine sulfinic acid, a sulfur-containg amino acid which was not detected in the CSF of the control group, was observed. One patient developed confluent white matter brain changes visible using MRI. This patient had the lowest concentration of S-adenosylmethionine in the CSF and carried two risk alleles for MTX neurotoxicity.

CONCLUSIONS

In this pilot study, MTX administered either intravenously or intraventricularly, induced marked biochemical alterations in the CSF. Whether these changes can be used to predict MTX-induced neurotoxicity at an early stage in treatment needs to be elucidated in larger clinical trials.

Effects of reduced glutathione (GSH) on oxaliplatin pharmacokinetics (OXA pk) and on Pt-DNA adducts formation in advanced colorectal cancer patients treated by FOLFOX4 regimen

2559

Background: Neurotoxicity is a common OXA toxicity in FOLFOX4 regimen for patients with advanced colorectal cancer. Recently, Cascinu et al. (JCO 2002; 20: 3478–3483) provided evidence that GSH reduces the OXA-induced neurotoxicity, but GSH influence on the formation of Pt-DNA adducts still remains unknown. This study evaluated the effect of GSH addition on OXA pk and on Pt-DNA adducts formation Table of Contents Methods: 28 patients were given twelve FOLFOX4 courses and randomized to receive either GSH 1,500 mg/m2 or normal saline solution (placebo) before OXA iv infusion. OXA pk and Pt-DNA adducts formation were evaluated at courses 5, 9 and 12. Total and ultrafiltered platinum were analyzed by atomic adsorption, Pt-DNA adducts in leukocytes (as model for tumour tissue) by adsorptive stripping voltammetry. Pk analysis were done by non-compartmental analysis, statistical analysis by non-parametric Mann-Whitney test. Results: Median total and ultrafiltered platinum median Cmax and AUCtot values were comparable to previously reported ones, being higher in the placebo arm, due to a moderate reduction of platinum clearance. The formation of Pt-DNA adducts was more pronounced in GSH arm (median value 20.3 Pt atoms/106 nucleotides vs. 5.7 Pt atoms/106 nucleotides), even not statistically significant. Conclusions: The addition of GSH to FOLFOX4 regimen is able to reduce the OXA-induced neurotoxicity, without affecting either the OXA pk behaviour or the formation of Pt-DNA adducts, without modifying FOLFOX4 clinical efficacy.

[Table: see text]

No significant financial relationships to disclose.

Plasma and tissue pharmacokinetics of epirubicin and Paclitaxel in patients receiving neoadjuvant chemotherapy for locally advanced primary breast cancer

The objective of the study was to assess individual distribution of antineoplastic drugs into the tumor. Twelve advanced-stage primary breast cancer patients with neoadjuvant epirubicin+paclitaxel chemotherapy were studied. Plasma concentrations of epirubicin and paclitaxel were monitored for 24 h. Epirubicin concentrations in subcutaneous and tumor tissues were measured using microdialysis up to 12 h postdose. Epirubicin concentrations were described by a compartmental population pharmacokinetic model (NONMEM). Noncompartmental analysis was used for paclitaxel. Plasma pharmacokinetics corresponded to published data. Mean epirubicin exposure in the tumor and in subcutaneous tissue was very similar, but tissue Cmax and area under the curve values reached only (means) 1% and 11%, respectively, of plasma values. Epirubicin doses were significantly correlated to tumor exposure irrespective of body surface area. There is no specific barrier for epirubicin to reach primary breast cancer tumors.

Evaluation of probe drugs and pharmacokinetic metrics for CYP2D6 phenotyping

INTRODUCTION

Cytochrome P450 2D6 (CYP2D6) is one of the most important enzymes catalyzing biotransformation of xenobiotics in the human liver. This enzyme's activity shows a high degree of interindividual variability caused in part by its genetic polymorphism, the so-called debrisoquine/sparteine polymorphism. The genetic component influencing CYP2D6 activity can be determined by genotyping. However, genotyping alone is not sufficient to accurately predict an individual's actual CYP2D6 activity, as this is also influenced by other factors. For the determination of the exact actual enzymatic activity ("phenotyping"), adequate probe drugs have to be administered prior to measurements of these compounds and/or their metabolites in body fluids. PROBE DRUGS: Debrisoquine, sparteine, metoprolol or dextromethorphan represent well-established probe drugs while tramadol has been recently investigated for this purpose. The enzymatic activity is reflected by various pharmacokinetic metrics such as the partial clearance of a parent compound to the respective CYP2D6-mediated metabolite or metabolic ratios. Appropriate metrics need to fulfill pre-defined validation criteria.

METHODS

In this review, we have compiled a list of such criteria useful to select the best metrics to reflect CYP2D6 activity. A comprehensive Medline search for reports on CYP2D6 phenotyping trials with the above mentioned probe drugs was carried out.

CONCLUSION

Application of the validation criteria suggests that dextromethorphan and debrisoquine are the best CYP2D6 phenotyping drugs, with debrisoquine having the problem of very limited availability as a therapeutic drug. However, the assessment of the best dextromethorphan CYP2D6 phenotyping metric/procedure is still ongoing.

Continuous or repeated prolonged cisplatin infusions in children: a prospective study on ototoxicity, platinum concentrations, and standard serum parameters

BACKGROUND

To overcome the ototoxicity of cisplatin, single bolus infusions were replaced by repeated prolonged infusions of lower doses or by continuous infusions at still lower infusion rates. However, considering ototoxicity little is, in fact, known about the tolerance of repeated prolonged or continuous infusion in children.

PROCEDURE

Auditory function was monitored along with plasma concentrations of free and total platinum (Pt), and with standard serum parameters (sodium, potassium, calcium, magnesium, phosphate, chloride, and creatinine) in 24 children receiving cisplatin by continuous infusion for the treatment of neuroblastoma and osteosarcoma or by repeated 1 or 6 hr infusions for the treatment of germ cell tumors.

RESULTS

Hearing deteriorated in 10/15 osteosarcoma patients, 2/3 neuroblastoma patients, and 1/6 patients with germ cell tumors. Ototoxicity occurred after cumulative doses between 120 and 360 mg/m(2) cisplatin. In osteosarcoma patients, ototoxicity was associated with a comparatively higher mean plasma concentration of free Pt. However, Pt plasma concentrations did not discriminate between patients with or without ototoxicity. In patients experiencing ototoxicity serum creatinine increased by 45% compared to pre-treatment levels (mean). Serum creatinine increased by 26% in patients without ototoxicity (P < 0.05, Mann-Whitney Rank sum test). Despite standardized hydration, discrete but significant changes of potassium, sodium, magnesium, and phosphate were observed during and/or after cisplatin infusion, which, however, did not discriminate between patients with and without ototoxicity.

CONCLUSIONS

While continuous cisplatin infusions are less nephrotoxic than repeated prolonged infusions, we observed considerable ototoxicity in patients treated with continuous cisplatin infusions, which necessitates further evaluations on the tolerance of continuous cisplatin infusions in children.

Ultratrace voltammetric determination of DNA-bound platinum in patients after administration of oxaliplatin

Oxaliplatin, a novel diaminocyclohexane-platinum complex, is used for the treatment of metastatic colorectal cancer. The amount of DNA-adduct formation of this drug in white blood cells of patients is determined after isolation of the DNA by density gradient centrifugation and a four-step solid phase extraction procedure. DNA is quantified by UV spectrometry, and platinum is determined after mineralization of the DNA sample by adsorptive stripping voltammetry (formazone method). It is possible to determine Pt-nucleotide ratios in clinical samples down to five Pt atoms in 10(8) nucleotides, and the dynamic range of the method covers three orders of magnitude. An absolute amount of 25 microg of DNA is sufficient for such measurements. With the method described, the time-dependent formation of oxaliplatin DNA adducts can be monitored in clinical studies, which may help us to understand inter-individual differences in the responses of patients to oxaliplatin-based therapy.

Individualised dosing strategy for high-dose carboplatin in patients with germ cell cancer

In contrast to conventional chemotherapy, carboplatin is still dosed per unit of body surface area (BSA) in high-dose chemotherapy protocols in clinical practice. To individualise dosing, a population pharmacokinetic model for poor-risk germ cell tumour patients receiving 1500 mg m(-2) carboplatin was developed. The typical central volume of distribution (19.9 l) and typical clearance (110 ml min(-1)) corresponded approximately to the extracellular fluid space or glomerular filtration rate, respectively. The covariate analysis identified several patient-specific factors. Carboplatin clearance was significantly related to creatinine clearance and body height, explaining 73% of the interindividual variability. Thus, an equation to predict individual clearance prior to treatment was developed (CL=0.41 x creatinine clearance+1.05 x body height-124.4). The relative frequency of developing toxicity increased significantly with higher AUC values for different types of toxicity. In addition, overall nonhaematological toxicity correlated significantly with exposure of carboplatin, leading to the assessment of a target AUC. Based on the prediction of individual clearance and the definition of a target AUC associated with moderate toxicity, an individualised dosing equation is proposed. Retrospectively, the individualised dosing strategy would have led to a higher dose on average and a broader range to be administered, compared to empirical dosing per unit BSA in the high-dose setting.

Bioequivalence investigation of high-dose etoposide and etoposide phosphate in lymphoma patients

PURPOSE

To compare etoposide pharmacokinetics following administration of high-dose etoposide and etoposide phosphate, a water-soluble prodrug of etoposide. Bioequivalence was assessed using a two-treatment randomized crossover design.

METHODS

Ten patients with high-risk or relapsed lymphoma were treated with a sequential high-dose chemotherapy. They were randomized to receive either 3 x 400 mg/m2 etoposide or an equimolar amount of etoposide phosphate (as 1-h infusions on three consecutive days) in the first course and the alternative drug in the second course. Serial plasma and ultrafiltered plasma samples were collected and analysed for etoposide by a reversed-phase HPLC method with UV and electrochemical detection. Pharmacokinetic parameters were estimated using a two-compartment model. Bioequivalence was assessed calculating the 90% confidence intervals (CI) for the ratios of the geometric means of AUC(0-infinity) and additionally of Cmax of etoposide derived from etoposide phosphate relative to etoposide in plasma and ultrafiltered plasma as point estimates (level of significance alpha < 0.05).

RESULTS

Pharmacokinetic parameters of etoposide were comparable in both treatment arms except that terminal half-life was significantly shorter and apparent Vss in ultrafiltered plasma was significantly larger following administration of the prodrug. The point estimates for AUC(0-infinity) of etoposide derived from etoposide phosphate relative to etoposide were 102.9% and 88.4% for plasma and ultrafiltered plasma, respectively. The 90% CIs were in the range from 80% to 125% where bioequivalence can be assumed. The point estimates of Cmax on day 3 of chemotherapy were 96.5% and 81.7% in plasma and ultrafiltrate with the 90% CI in ultrafiltered plasma being out of the range from 80% to 125%.

CONCLUSION

With respect to total drug exposure, represented by AUC(0-infinity), high-dose etoposide phosphate is bioequivalent to high-dose etoposide.

Feasibility of intraventricular administration of etoposide in patients with metastatic brain tumours

As the systemic administration of etoposide is effective in the treatment of relapsed and metastatic brain tumours, a pilot trial was designed to study the feasibility of intraventricular administration of etoposide in such patients. 14 patients aged 2.1 to 33.2 years were treated with intraventricular etoposide simultaneously with either oral or intravenous chemotherapy with trofosfamide or carboplatin and etoposide. In 59 courses (1-12/patient) 0.5 mg etoposide was administered daily via an indwelling subcutaneous reservoir for 5 consecutive days every 2-5 weeks over a period of 0-11 months. During 15 courses in 5 patients serial CSF samples were obtained and etoposide levels were determined by reversed-phase HPLC. Side effects included transient headache and bacterial meningitis, each during 2 courses. Pharmacokinetic data analysis in the CSF (11 courses, 4 patients) revealed a terminal half-life of 7.4+/-1.2 hours and an AUC of 25.0 +/- 9.5 microg h ml(-1)(mean +/- standard deviation). The volume of distribution at steady state and total clearance exhibited a large interindividual variability with mean values of 0.16 l and 0.46 ml min(-1)respectively. Intraventricularly administered etoposide is well tolerated. CSF peak levels exceed more than 100-fold those achieved with intravenous infusions. Further studies should be focused on optimizing the dose and schedule and on determining the effectiveness of intraventricularly administered etoposide.

Separation and identification of platinum adducts with DNA nucleotides by capillary zone electrophoresis and capillary zone electrophoresis coupled to mass spectrometry

Platinum adducts are supposed to be the cytotoxic lesions in DNA after platinum-containing anticancer therapy. Various adducts are formed upon interaction of platinum complexes with nucleotides, but contribution of individual adducts to antitumor activity and toxicity of platinum complexes still remains to be examined. A capillary zone electrophoresis (CZE) method is described that is suitable to separate individual platinum adducts. We investigated the formation of adducts following the reaction of cis-diamminedichloroplatinum (II) (cisplatin) with various DNA nucleotides. Baseline separation of unmodified and modified nucleotides (adducts) was achieved using uncoated fused-silica capillaries and basic separation buffers. In order to elucidate the observed peak pattern, a coupled CZE-electrospray ionization-mass spectrometry (ESI)-MS approach was applied. After incubation of mononucleotides with cisplatin, monochloro, monoaqua and bifunctional adduct species were detected. Consequently, the migration order of nucleotides and individual platinum adducts could be determined. Moreover, the time-dependent conversion from monochloro to monoaqua and subsequently to bifunctional adducts was monitored. In conclusion, individual platinum adducts were separated by CZE and identified by CZE-ESI-MS. Formation and conversion of distinct species were confirmed. Potential applications comprise studies of novel platinum complexes, investigations of platinum-adduct formation with DNA, and determination of platinum-DNA adducts in cells.

Determination of platinum complexes in clinical samples by a rapid flameless atomic absorption spectrometry assay

The frequent use of platinum (Pt) complexes in cancer chemotherapy and the application of new therapeutic options and dosing strategies have increased the need for rapid analytic procedures to determine Pt concentrations in the biologic fluids of patients. Therefore a flameless atomic absorption spectrometry method for the quantification of Pt in plasma and ultrafiltrate was developed and validated. A simple sample preparation of only one dilution step was established. Only 400 microL of whole blood was required for duplicate analysis of Pt in both matrices. The matrix-specific temperature programs took less than 75 seconds. The lower limit of quantification was 40 ng Pt/mL and 20 ng Pt/mL for plasma and ultrafiltrate, respectively. Suitable linearity could be reached using separate calibration curves for the high and low Pt concentration ranges. Recovery of Pt was complete, and there were no major stability problems. The accuracy and precision of the new method met the international criteria for the validation of bioanalytic methods. In addition, the use of different anticoagulants for clinical sampling, ultrafiltration systems, and ultrafiltration conditions were investigated. The assay has already been extensively applied to pharmacokinetic studies. In conclusion, the new Pt assay proved to be rapid, simple, sensitive, and suitable for clinical use.

Pharmacokinetic and pharmacodynamic comparison of two doses of calcium folinate combined with continuous fluorouracil infusion in patients with advanced colorectal cancer

The optimum dose of calcium folinate (leucovorin) as modulator of fluorouracil has not been defined yet. We conducted a randomized trial to compare the pharmacokinetics/pharmacodynamics of two doses of calcium folinate. 16 patients with advanced colorectal cancer were treated with 650 mg/m2/d fluorouracil as 5 day continuous infusion and randomized to receive either 20 mg/m2 or 100 mg/m2 calcium folinate as short infusion twice daily. The two diastereoisomers of calcium folinate were analyzed separately by chiral HPLC to account for differences in their pharmacokinetics. The pharmacokinetics of fluorouracil was not affected by folinate dosing. Total clearance of the active (6S)-diastereoisomer was found to be lower after the higher dose of folinate which can be explained by nonlinear metabolism. The incidence of treatment-induced mucositis significantly increased with (6S)-folinate exposure, whereas fluorouracil exposure was not related to this type of toxicity. In conclusion, exposure to folinate is more important for toxicity in this regimen than fluorouracil pharmacokinetics. Therefore, monitoring of fluorouracil plasma levels is not useful in this combination. Our results show that folinate dose should be carefully selected. Lower doses of folinate might be preferred because of less toxicity compared to higher doses.

Determination of cyclophosphamide and its metabolites in human plasma by high-performance liquid chromatography-mass spectrometry

A sensitive HPLC-MS method was developed for the simultaneous determination of cyclophosphamide and its metabolites 4-hydroxycyclophosphamide (aldocyclophosphamide), 4-ketocyclophosphamide, caboxyphosphamide and 3-dechloroethylifosfamide in human plasma. 4-Hydroxycyclophosphamide was converted with methylhydroxylamine to the stable methyloxime form. We used a solid-phase extraction with C18 cartridges followed by HPLC-MS with the single mass spectrometer SSQ 7000 of Finnigan. The limits of detection were 15 ng/ml for cyclophosphamide, 3-dechloroethylifosfamide and ketocyclophosphamide in each case and 30 ng/ml for carboxyphosphamide and 4-hydroxycyclophosphamide, respectively. First results of pharmacokinetics are shown.

Utility of isotachophoresis-capillary zone electrophoresis, mass spectrometry and high-performance size-exclusion chromatography for monitoring of interleukin-6 dimer formation

The utility of isotachophoresis-capillary zone electrophoresis (ITP-CZE) and high-performance size-exclusion chromatography (HPSEC) was investigated for determination of dimeric and monomeric recombinant human interleukin-6 (rhIL-6). Using ITP-CZE heterogeneity of dimeric rhIL-6 could be revealed resolving two peaks in the electropherograms, while with HPSEC dimeric rhIL-6 eluted as one homogeneous fraction. Both protein forms were monitored during incubation of monomeric rhIL-6 at different pH and temperature. The selectivity of counterflow ITP-CZE in conjunction with the low concentration determination limits enabled reanalysis of HPSEC fractions for identification of the dimer in the electropherograms. Both ITP-CZE and HPSEC were shown to be suitable to monitor the dimerization of rhIL-6, similar monomer-to-dimer peak area ratios were obtained throughout the incubation. Dimer formation kinetics increased with decreasing pH and with increasing temperature, it was entirely suppressed at neutral pH and room temperature. In contrast to HPSEC, ITP-CZE enabled separation of further still unidentified artifacts apparently formed during incubation of rhIL-6. CZE analysis in conjunction with electrospray ionization mass spectrometry revealed the non-covalent binding character of the dimeric rhIL-6 complex and facilitated interpretation of the electropherograms.

Monitoring of chemotherapy-induced proteinuria using capillary zone electrophoresis

Capillary zone electrophoresis (CZE) was investigated for its suitability to monitor proteinuria occurring during nephrotoxic drug therapy. Urine samples of tumor patients receiving chemotherapy consisting of carboplatin, etoposide, and ifosfamide were concentrated and desalted in microconcentrators and analyzed in two different alkaline CZE buffer systems. Reduction of electroosmotic flow (EOF) by the addition of putrescine increased the number of resolved protein peaks. Both CZE methods were linear between 2.5 and 50 microg/ml, exhibited satisfactory precision (relative standard deviation <10%) and were suitable for monitor the time course of proteinuria after chemotherapy administration. In contrast to sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), CZE detected interindividual differences in protein patterns. Whereas these differences hampered a direct quantification of proteins in urine, they may contain information on the type or extent of kidney damage.

Quantitative trace analysis of interleukin-3, interleukin-6, and basic model proteins using isotachophoresis-capillary zone electrophoresis with hydrodynamic counterflow

A quantitative analytical technique to determine trace concentrations of recombinant human interleukin-3 (rhIL-3), recombinant human IL-6 (rhIL-6), and various basic model proteins is described using isotachophoresis-capillary zone electrophoresis (ITP-CZE). Proteins were separated on coated fused-silica capillaries using a commercial capillary electrophoretic system modified for the application of isotachophoretic preconcentration with hydrodynamic counterflow. The effect of injection time and isotachophoretic focusing time was investigated and compared with predictions from existing mathematical models. Good linearity of the calibration graphs (r > 0.995) was observed for all investigated proteins. The limit of quantification was in the 10(-8) M range using UV detection at 200 nm. Within-day and between-day precision of peak area ranged between 1 and 6%. Precision was unaffected by isotachophoretic preconcentration. In conclusion, the described method is feasible to quantify trace concentrations of rhIL-3, rhIL-6, and basic proteins. Potential applications comprise issues of pharmaceutical quality control.

Determination of the cytotoxic catechol metabolite of etoposide (3'O-demethyletoposide) in human plasma by high-performance liquid chromatography

The anticancer drug etoposide undergoes O-demethylation in humans. The formed catechol metabolite exhibits significant cytotoxic activity. A simple, rapid, selective, and sensitive reversed-phase high-performance liquid chromatography assay was developed for the measurement of etoposide catechol in plasma of tumour patients. The metabolite was quantified using electrochemical detection. Ascorbic acid was added to each sample to prevent oxidation of etoposide catechol during sample preparation. Linear responses were obtained between 40 ng/ml and 1.25 microg/ml with correlation coefficients exceeding 0.991. The detection limit was 10 ng/ml. Recovery, within-day precision, between-day precision and accuracy were satisfactory. The method has been applied to characterize the concentration-time profile of etoposide catechol in plasma of tumour patients following administration of high-dose etoposide.

Five-day continuous infusion of 5-fluorouracil and pulsed folinic acid in patients with metastatic colorectal carcinoma: an effective second-line regimen

OBJECTIVE

A previous phase I trial in 14 pretreated patients with progressive advanced colorectal cancer demonstrated 750 mg/m2 to be the maximum tolerable dose of 5-fluorouracil (5-FU) administered as a five-day continuous infusion modulated by short infusions of 100 mg/m2 folinic acid twice daily. The dose-limiting toxicities were hand-foot syndrome and severe mucositis. A response rate of 21% and 50% stable disease could be achieved. In order to determine the effectiveness and tolerability, we initiated a multicenter phase II trial applying a 650 mg/m2 recommended dose of 5-FU and 100 mg/m2 folinic acid twice daily every three weeks.

PATIENTS AND METHODS

From January 1994 to July 1996, 88 advanced and progressive colorectal cancer patients either previously treated with a bolus schedule of 5-FU and folinic acid (34 patients) or without (54 patients) previous chemotherapy were included in this trial.

RESULTS

In the group of previously treated patients, therapy led to 6% (2 of 34 patients) remissions while stable disease could be observed in 68% (23 of 34 patients) of the patients. The median survival time was 14 months. The main toxicity was mucositis grade 3 in 15% of the previously treated patients and 10% in the nonpretreated patients. In the population of nonpretreated patients, the overall response rate was 15% (eight of 54 patients) and stable disease could be induced in 67% (36 of 54 patients). The median survival time was 13.7 months.

CONCLUSION

This regimen is an active second-line therapy in advanced colorectal cancer with minimal toxicity, thus preserving the quality of life during palliative chemotherapy. Antitumor activity in previously untreated patients does not seem superior to that obtained with weekly regimens applying 24- or 48-hour continuous infusions of 5-FU and folinic acid.