A randomized study of epirubicin at four different dose levels in advanced breast cancer. Feasibility of myelotoxicity prediction through single blood-sample measurement

Epirubicin for the Treatment of Sepsis and Septic Shock (EPOS-1): study protocol for a randomised, placebo-controlled phase IIa dose-escalation trial

INTRODUCTION

Sepsis remains the major cause of death among hospitalised patients in intensive care. While targeting sepsis-causing pathogens with source control or antimicrobials has had a dramatic impact on morbidity and mortality of sepsis patients, this strategy remains insufficient for about one-third of the affected individuals who succumb. Pharmacological targeting of mechanisms that reduce sepsis-defining organ dysfunction may be beneficial. When given at low doses, the anthracycline epirubicin promotes tissue damage control and lessens the severity of sepsis independently of the host-pathogen load by conferring disease tolerance to infection. Since epirubicin at higher doses can be myelotoxic, a first dose-response trial is necessary to assess the potential harm of this drug in this new indication.

METHODS AND ANALYSIS

Epirubicin for the Treatment of Sepsis and Septic Shock-1 is a randomised, double-blind, placebo-controlled phase 2 dose-escalation phase IIa clinical trial to assess the safety of epirubicin as an adjunctive in patients with sepsis. The primary endpoint is the 14-day myelotoxicity. Secondary and explorative outcomes include 30-day and 90-day mortality, organ dysfunction, pharmacokinetic/pharmacodynamic (PK/PD) and cytokine release. Patients will be randomised in three consecutive phases. For each study phase, patients are randomised to one of the two study arms (epirubicin or placebo) in a 4:1 ratio. Approximately 45 patients will be recruited. Patients in the epirubicin group will receive a single dose of epirubicin (3.75, 7.5 or 15 mg/m2 depending on the study phase. After each study phase, a data and safety monitoring board will recommend continuation or premature stopping of the trial. The primary analyses for each dose level will report the proportion of myelotoxicity together with a 95% CI. A potential dose-toxicity association will be analysed using a logistic regression model with dose as a covariate. All further analyses will be descriptive.

ETHICS AND DISSEMINATION

The protocol is approved by the German Federal Institute for Drugs and Medical Devices. The results will be submitted for publication in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT05033808.

Pharmacodynamic modeling of adverse effects of anti-cancer drug treatment

Purpose

Adverse effects related to anti-cancer drug treatment influence patient’s quality of life, have an impact on the realized dosing regimen, and can hamper response to treatment. Quantitative models that relate drug exposure to the dynamics of adverse effects have been developed and proven to be very instrumental to optimize dosing schedules. The aims of this review were (i) to provide a perspective of how adverse effects of anti-cancer drugs are modeled and (ii) to report several model structures of adverse effect models that describe relationships between drug concentrations and toxicities.

Methods

Various quantitative pharmacodynamic models that model adverse effects of anti-cancer drug treatment were reviewed.

Results

Quantitative models describing relationships between drug exposure and myelosuppression, cardiotoxicity, and graded adverse effects like fatigue, hand-foot syndrome (HFS), rash, and diarrhea have been presented for different anti-cancer agents, including their clinical applicability.

Conclusions

Mathematical modeling of adverse effects proved to be a helpful tool to improve clinical management and support decision-making (especially in establishment of the optimal dosing regimen) in drug development. The reported models can be used as templates for modeling a variety of anti-cancer-induced adverse effects to further optimize therapy.

Pharmacokinetics and pharmacodynamics of dasatinib in the chronic phase of newly diagnosed chronic myeloid leukemia

PURPOSE

Dasatinib is a novel, oral, multi-targeted kinase inhibitor of breakpoint cluster region-abelson (BCR-ABL) and Src family kinases. The study investigated pharmacokinetic (PK) and pharmacodynamic (PD) analyses of dasatinib in 51 newly diagnosed, chronic phase, chronic myeloid leukemia patients.

METHODS

The dasatinib concentration required to inhibit 50 % of the CrkL (CT10 regulator of kinase like) phosphorylation in bone marrow CD34+ cells (half maximal (50 %) inhibitory concentration (IC50)CD34+cells) was calculated from each patient's dose-response curve using flow cytometry. PK parameters were obtained from the population pharmacokinetic analysis of dasatinib concentrations in plasma on day 28 after administration.

RESULTS

Early molecular responses were not significantly associated with PK or PD (IC50 CD34+cells) parameters. However, the PK/PD parameter-time above IC50 CD34+cells-significantly correlated with BCR-ABL transcript level at 3 months (correlation coefficient (CC) = -0.292, P = 0.0375) and the reduction of BCR-ABL level at 1 or 3 months (CC = -0.404, P = 0.00328 and CC = -0.356, P = 0.0104, respectively). Patients with more than 12.6 h at time above IC50 CD34+cells achieved a molecular response of 3.0 log reduction at 3 months and those more than 12.8 h achieved a deep molecular response less than 4.0 log reduction at 6 months at a significantly high rate (P = 0.013, odds ratio = 4.8 and P = 0.024, odds ratio = 4.3, respectively).

CONCLUSION

These results suggest that the anti-leukemic activity of dasatinib exhibits in a time-dependent manner and that exposure for more than 12.8 h at time above IC50 CD34+cells could significantly improve prognosis.

Dose schedule optimization and the pharmacokinetic driver of neutropenia

Toxicity often limits the utility of oncology drugs, and optimization of dose schedule represents one option for mitigation of this toxicity. Here we explore the schedule-dependency of neutropenia, a common dose-limiting toxicity. To this end, we analyze previously published mathematical models of neutropenia to identify a pharmacokinetic (PK) predictor of the neutrophil nadir, and confirm this PK predictor in an in vivo experimental system. Specifically, we find total AUC and Cmax are poor predictors of the neutrophil nadir, while a PK measure based on the moving average of the drug concentration correlates highly with neutropenia. Further, we confirm this PK parameter for its ability to predict neutropenia in vivo following treatment with different doses and schedules. This work represents an attempt at mechanistically deriving a fundamental understanding of the underlying pharmacokinetic drivers of neutropenia, and provides insights that can be leveraged in a translational setting during schedule selection.

Dose-tailoring of FEC adjuvant chemotherapy based on leukopenia is feasible and well tolerated. Toxicity and dose intensity in the Scandinavian Breast Group phase 3 adjuvant Trial SBG 2000-1

The SBG 2000-1 trial is a randomised study that investigates if dose-tailored adjuvant FEC therapy based on the individual's leukocyte nadir value can improve outcome. The study has included 1535 women with medium and high-risk breast cancer.

PATIENTS AND METHODS

After a first standard dosed FEC course (5-fluorouracil 600 mg/m(2), epirubicin 60 mg/mg(2) and cyclophosphamide 600 mg/m(2)), patients who did not reach leukopenia grade III or IV were randomised to standard doses (group standard) or doses tailored to achieve grade III leukopenia (group tailored) at courses 2-7. Patients who achieved leukopenia grade III or more after the first course were not randomised but continued on standard doses (group registered).

RESULTS

Both planned and actually delivered number of courses (seven) were the same in all three arms. The relative dose intensity was increased by a factor of 1.31 (E 1.22, C 1.43) for patients in the tailored arm compared to the expected on standard dose. Ninety percent of the patients in the tailored arm achieved leukopenia grade III-IV compared with 29% among patients randomised to standard dosed therapy. Dose tailoring was associated with acceptable acute non-haematological toxicity with more total alopecia, nausea, vomiting and fatigue.

CONCLUSION

Dose tailoring according to leukopenia was feasible. It led to an increased dose intensity and was associated with acceptable excess of acute non-haematological toxicity.

Mechanism-based Pharmacokinetic/Pharmacodynamic Meta-analysis of Trabectedin (ET-743, Yondelis) Induced Neutropenia

Myelosuppression was found to be one of the main toxicities of trabectedin (ET-743, Yondelis) during phase I/II studies. Our objective was to develop a pharmacokinetic-pharmacodynamic (PK/PD) model that describes the time course of the absolute neutrophil counts (ANCs) in cancer patients receiving trabectedin. Data from 699 patients who received intravenous trabectedin as monotherapy (dose range: 0.006-1.8 mg/m2) as a 1-, 3-, or 24-h infusion every 21 days; 1- or 3-h infusion on days 1, 8, and 15 every 28 days; or a 1-h infusion daily for 5 consecutive days every 21 days were used to develop (N=405; ANCs=7,291) and validate (N=294; ANCs=5,029) the model. The PK/PD model comprised a trabectedin-sensitive progenitor cell compartment, linked to the peripheral blood compartment, through three transition compartments representing the maturation chain in the bone marrow. To capture the rebound effect due to endogenous growth factors, the model included a feedback mechanism. The model estimated three system-related parameters: ANC at baseline (Circ0), mean transit time in bone marrow (MTT), and a feedback parameter (gamma). A first-order process quantified by the rate constant k(e0) described the trabectedin concentrations at the effect compartment (C(e)), which were assumed to reduce the proliferation rate and/or to increase the killing rate of the progenitor cells according to the function alphaC(e)beta. The model was qualified and simulations were undertaken to evaluate the neutropenia schedule dependency and the effects of selected covariates. NONMEM software was used to perform the modeling and simulation analyses. For a typical man of 70 kg, the mean values (between-subject variability; %) of the Circ0, MTT, gamma, k(e0), alpha, and beta were estimated to be 4.46 x 10(9)/l (37.9%), 4.0 days (37.5%), 0.218 (41.8%), 2.09 h(-1) (77.9%), 2.00 l/microg (85.1%), and 1.26, respectively. Although in women, k(e0) was reduced by 29% and a 25% increase in body weight resulted in a 12.6% reduction in the beta parameter, the clinical relevance of these effects is limited. The model evaluation procedure indicated accurate prediction of the observed incidence of neutropenia grades 3 and 4 across the dosing regimens evaluated. Simulations indicated that trabectedin dose and interdose interval, but not infusion duration, are the main determinants of the neutropenia severity. The model-predicted time course of the ANC and its variability confirmed that neutropenia is reversible, of short duration, and non-cumulative. The extent and time course of neutropenia following six different dosing regimens of trabectedin were well predicted by the semiphysiological PK/PD model.

International Society of Geriatric Oncology Chemotherapy Taskforce: evaluation of chemotherapy in older patients--an analysis of the medical literature

The elderly comprise the majority of patients with cancer and are the recipients of the greatest amount of chemotherapy. Unfortunately, there is a lack of data to make evidence-based decisions with regard to chemotherapy. This is due to the minimal participation of older patients in clinical trials and that trials have not systematically evaluated chemotherapy. This article reviews the available information with regard to chemotherapy and aging provided by a task force of the International Society of Geriatric Oncology (SIOG). Due to the lack of prospective data, the conclusions and recommendations made are a consensus of the participants. Extrapolation of data from younger to older patients is necessary, particularly to those patients older than 80 years, for which data is almost entirely lacking. The classes of drugs reviewed include alkylators, antimetabolites, anthracyclines, taxanes, camptothecins, and epipodophyllotoxins. Clinical trials need to incorporate an analysis of chemotherapy in terms of the pharmacokinetic and pharmacodynamic effects of aging. In addition, data already accumulated need to be reanalyzed by age to aid in the management of the older cancer patient.

Individually tailored toxicity-based 5-fluorouracil, epirubicin and cyclophosphamide (FEC) therapy of metastatic breast cancer

Chemotherapy dosing only based on body surface area (BSA) results in marked pharmacokinetic and toxicity variations, which may result in an inferior outcome for some patients. A toxicity-based dosing schedule for individually tailored treatment with granulocyte colony-stimulating factor (G-CSF) supported 5-fluorouracil (F), epirubicin (E) and cyclophosphamide (C) (dFEC) was developed and studied in patients with metastatic breast cancer with the purpose to determine its efficiency and toxicity. Twenty-six women, median age 48 years, were included and the individual E and C doses were tailored stepwise based on the recorded hematological toxicity. Twenty-one patients (81%; 95% confidence interval (CI), 66% to 96%) had an objective response, including six complete responses (23%; CI, 7%-39%). At median follow-up of 113 months, the median time to progression and median overall survival were 14 and 36 months, respectively. The delivered dose intensity was high but varied substantially between patients (ranges F 126-202, E 14.4-36.0, C 160-510 mg/m(2)/w). The dominating grade III/IV toxicity was nausea (12% of patients) and febrile neutropenia (31% of patients). The tailored and dose-escalated FEC was highly active and feasible in metastatic breast cancer and may provide a pragmatic way of overcoming the shortcomings of standard BSA-based dosing.

Assessment of the validity of a population pharmacokinetic model for epirubicin

AIMS

The aim of this study was to evaluate a population model for epirubicin clearance using internal and external validation techniques.

METHODS

Jackknife samples were used to identify outliers in the population dataset and individuals influencing covariate selection. Sensitivity analyses were performed in which serum aspartate transaminase (AST) values (a covariate in the population model) or epirubicin concentrations were randomly changed by +/-10%. Cross-validation was performed five times, on each occasion using 80% of the data for model development and 20% to assess the performance of the model. External validation was conducted by assessing the ability of the population model to predict concentrations and clearances in a separate group of 79 patients.

RESULTS

Structural parameter estimates from all jackknife samples were within 7.5% of the final population estimates and examination of log likelihood values indicated that the selection of AST in the final model was not due to the presence of outliers. Alteration of AST or epirubicin concentrations by +/-10% had a negligible effect on population parameter estimates and their precision. In the cross-validation analysis, the precision of clearance estimates was better in patients with AST concentrations>150 U l-1. In the external validation, epirubicin concentrations were over-predicted by 81.4% using the population model and clearance values were also poorly predicted (imprecision 43%).

CONCLUSIONS

The results of internal validation of population pharmacokinetic models should be interpreted with caution, especially when the dataset is relatively small.

Dose adaptation of antineoplastic drugs in patients with liver disease

Dose adaptation for liver disease is important in patients treated with antineoplastic drugs because of the high prevalence of impaired liver function in this population and the dose-dependent, frequently serious adverse effects of these drugs. We classified the antineoplastic drugs marketed in Switzerland at the end of 2004 according to their bioavailability and/or hepatic extraction to predict their kinetic behaviour in patients with decreased liver function. This prediction was compared with kinetic studies carried out with these drugs in patients with liver disease. The studies were identified by a structured, computer-based literature search. Of the 69 drugs identified, 52 had a predominant extrarenal (in most cases hepatic) metabolism and/or excretion. For 49 drugs, hepatic extraction could be calculated and/or bioavailability data were available, allowing classification according to hepatic extraction. For 18 drugs, kinetic studies have been reported in patients with impaired liver function, with the findings generally resulting in quantitative recommendations for adaptation of the dosage. In particular, recommendations are precise for 16 drugs excreted by the bile (e.g. doxorubicin and derivatives and vinca alkaloids). Validation studies comparing such recommendations with kinetics and/or dynamics of antineoplastic drugs in patients with decreased liver function have not been published. We conclude that there are currently not enough data for safe use of cyctostatics in patients with liver disease. Pharmaceutical companies should be urged to provide kinetic data (especially hepatic extraction data) for the classification of such drugs and to conduct kinetic studies for drugs with primarily hepatic metabolism in patients with impaired liver function to allow quantitative advice to be given for dose adaptation.

Population analysis of the pharmacokinetics and the haematological toxicity of the fluorouracil-epirubicin-cyclophosphamide regimen in breast cancer patients

PURPOSE

The aims of the study were (a) to characterise the pharmacokinetics (PK), including inter-individual variability (IIV) and inter-occasion variability (IOV) as well as covariate relationships and (b) to characterise the relationship between the PK and the haematological toxicity of the component drugs of the fluorouracil (5-FU)-epirubicin (EPI)-cyclophosphamide (CP) regimen in breast cancer patients.

PATIENTS AND METHODS

Data from 140 breast cancer patients, either within one of different studies or in routine clinical management, were included in the analyses. The patients were all treated with the fluorouracil-epirubicin-cyclophosphamide (FEC) regimen every third week for 3-12 courses, either in standard doses, i.e. 600/60/600 mg/m(2) of 5-FU, EPI and CP, respectively, or according to a dose escalation/reduction protocol (tailored dosing). PK data were available from 84 of the patients, whereas time-courses of haematological toxicity were available from 87 patients. The data analysis was carried out using mixed effects models within the NONMEM program.

RESULTS

The PK of 5-FU, EPI and 4-hydroxy-cyclophosphamide (4-OHCP), the active metabolite of CP, were described with a one-compartment model with saturable elimination, a three-compartment linear model and a two-compartment linear model, respectively. No clinical significant correlation was found between PK across drugs. The unexplained variability in clearance was found to be less within patients, between courses (inter-occasion variability, IOV) than between patients (inter-individual variability, IIV) for EPI and 5-FU. For 4-OHCP, however, the IIV diminished by approximately 45% when significant covariates were included and the final population model predicts an IIV that is equal to IOV. Significant covariates for elimination capacity parameters were serum albumin (5-FU, EPI and 4-OHCP), creatinine clearance (5-FU), bilirubin (EPI) and body surface area (BSA) (4-OHCP). Elimination capacity of 5-FU and EPI was not related to BSA and for none of the studied drugs did body weight explain the PK variability. The time-course of haematological toxicity after treatment was well described by a semi-physiological model that assumes additive haematological toxicity between CP and EPI with negligible contribution from 5-FU. The influence of G-CSF could be incorporated into the model in a mechanistic manner as shortening the maturation time to 43% of the normal duration and increasing the mitotic activity to 269% of normal activity.

CONCLUSIONS

The models presented describe the dose-concentration-toxicity relationships for the FEC therapy and may provide a basis for implementation and comparison of different individualisation strategies based on covariates, therapeutic drug monitoring and/or pharmacodynamic (PD) feedback. The PD model extends on previous semi-mechanistic models in that it also takes G-CSF administration into account.

Pharmacokinetic variability of anticancer agents

The translation of advances in cancer biology to drug discovery can be complicated by pharmacokinetic variation between individuals and within individuals, and this can result in unpredictable toxicity and variable antineoplastic effects. Previously unrecognized variables (such as genetic polymorphisms) are now known to have a significant impact on drug disposition. How can the pharmacokinetic variability of anticancer agents be reduced? This will require the understanding of correlations between pharmacokinetics and treatment outcomes, the identification of relevant patient parameters, mathematical modelling of individual and population pharmacokinetics, and the development of algorithms that will tailor doses to the individual patient.

Model Describing the Relationship Between Pharmacokinetics and Hematologic Toxicity of the Epirubicin-Docetaxel Regimen in Breast Cancer Patients

Purpose

The aims of the present study were (1) to characterize the pharmacokinetics of both component drugs and (2) to describe the relationship between the pharmacokinetics and the dose-limiting hematologic toxicity for the epirubicin (EPI)/docetaxel (DTX) regimen in breast cancer patients.

Patients and Methods

Forty-four patients with advanced disease received EPI and DTX every 3 weeks for up to nine cycles. The initial doses (EPI/DTX) were 75/70 mg/m2. Based on leukocyte (WBC) and platelet counts, the subsequent doses were, stepwise, either escalated (maximum, 120/100 mg/m2) or reduced (minimum, 40/50 mg/m2). Hematologic toxicity was monitored in all patients, whereas pharmacokinetics was studied in 16 patients. A semiphysiological model, including physiological parameters as well as drug-specific parameters, was used to describe the time course of WBC count following treatment.

Results

In the final pharmacokinetic model, interoccasion variability was estimated to be less than interindividual variability in the clearances for both drugs. The sum of the individual EPI and DTX areas under concentration-time curve correlated stronger to WBC survival fraction than did the corresponding sum of doses. A pharmacokinetic-pharmacodynamic (PK-PD) model with additive effects of EPI and DTX could adequately describe the data.

Conclusion

The final PK-PD model might provide a tool for calculation of WBC time course, and hence, for prediction of nadir day and duration of leukopenia in breast cancer patients treated with the EPI/DTX regimen.

Maximum a posteriori Bayesian estimation of epirubicin clearance by limited sampling

AIMS

To develop a limited sampling strategy for estimation of epirubicin clearance.

METHODS

The data set comprised 1051 concentrations measured in 105 patients with advanced or metastatic breast cancer treated with epirubicin alone. Ten limited sampling designs comprising two or three blood samples were proposed, taken at times identified by D-optimality from population pharmacokinetic parameter estimates. The data set was then truncated to include the sampling times for each of the designs. MAP Bayesian estimates of clearance were generated for each design and compared with clearance estimates obtained using all the data. The limited sampling designs were also validated using a separate data set obtained from 18 patients with either breast cancer or hepatocellular carcinoma. The sensitivity of the best limited sampling designs to sample time recording errors of 0-10% or 10-20% was then assessed using a simulated data set including 200 patients.

RESULTS

The optimum sampling times were: end of the injection and 18 min, 40 min, 3 h, 10 h and 48 h after the start of the injection. The best three-sample design included samples at 40 min, 3 h and 48 h and gave unbiased estimates of clearance with an imprecision of 9.1% (95% CI 7.3, 10.5). The best two sample design included samples at 3 and 48 h and gave unbiased estimates of clearance with an imprecision of 12.4% (95% CI 9.6, 14.6). Using the validation data set, these two and three sample designs gave unbiased estimates of clearance with an imprecision of 5.6% (95% CI 3.7, 7.0) and 4.2% (95% CI 2.6, 5.3), respectively. Simulations that included 0-10% or 10-20% errors in the recording of the blood sampling times had negligible effects on the bias and imprecision of clearance estimates.

CONCLUSIONS

Limited sampling designs have been identified and validated that estimate epirubicin clearance with adequate precision and without bias from two or three blood samples. These designs also allow flexibility in blood sample collection and are robust with regard to sample time recording errors.

Pharmacokinetics and pharmacodynamics of imatinib in a phase I trial with chronic myeloid leukemia patients

PURPOSE

To evaluate the basic pharmacokinetic (PK) characteristics of imatinib mesylate and assess the relationship between the PK and pharmacodynamic (PD) properties of the drug.

PATIENTS AND METHODS

The PK and PD properties of imatinib were investigated during a phase I trial that included 64 adult patients with Philadelphia chromosome-positive leukemias. Patients received imatinib orally once or twice daily. PK parameters of imatinib, derived from the plasma concentration-time curves, were determined. PD response, defined as the WBC after 1 month of treatment with imatinib, was used to develop an efficacy model. A maximum inhibition-effect model was used to describe the relationship between reduction in WBC and drug exposure parameters.

RESULTS

Imatinib exposure was dose proportional after oral administration for the dose range of 25 to 1,000 mg. There was a 1.5- to three-fold drug accumulation after repeated once-daily dosing. Mean plasma trough concentration was 0.57 microg/mL (approximately 1 micromol/L) 24 hours after administration of 350 mg of imatinib at steady-state, which exceeds the 50% inhibitory concentration required to inhibit proliferation of Bcr-Abl-positive leukemic cells. Analysis of PK/PD relationships indicates that the initial hematologic response depends on the administered dose for patients with chronic myeloid leukemia.

CONCLUSION

Drug exposure (area under the concentration-time curve) is dose proportional for the dose range of 25 to 1,000 mg, and there is a 1.5- to three-fold drug accumulation at steady-state after once-daily dosing. Analysis of the relationship between PD (WBC reduction) and PK parameters at steady-state indicates that a dose of 400 mg or greater is required for maximal PD effect.

A population model of epirubicin pharmacokinetics and application to dosage guidelines

PURPOSE

To use a population approach to identify readily available clinical or biochemical characteristics that influence the pharmacokinetics of epirubicin and to develop new dosage guidelines based on these results.

METHODS

Data were available from 109 patients with advanced breast cancer, 72 of whom were known to have liver metastases. They were treated with single-agent epirubicin 12.5 to 120 mg/m(2). Analysis was performed using the software package NONMEM and a three-compartment model was fitted to the data.

RESULTS

Individual clearance (CL) estimates ranged from 4 to 86 l/h and the final model included CL as a function of aspartate aminotransferase (AST): CL (l/h)=72.9-(72.9x0.135xlnAST). Inclusion of this factor reduced the interindividual variability in CL from 49% to 39%. Using a target AUC of 4000 ng.h/ml, the following doses were predicted to achieve this exposure with the greatest precision: AST <150 IU/l 125 mg; AST 150-250 IU/l 90 mg; AST 250-500 IU/l 60 mg; AST >500 IU/l 30 mg. These new guidelines were compared with three other guidelines based on serum bilirubin or AST concentrations and body surface area (BSA). The new guidelines achieved the target with greater precision (root mean squared error, rmse, 39.0%) than the current UK guidelines, current USA guidelines or an earlier equation based on AST (rmse 63%, 62% and 59%, respectively).

CONCLUSIONS

The proposed dosing guidelines should reduce variability in systemic exposure to epirubicin more effectively than traditional approaches. In addition, as they do not require adjustment according to BSA, they could reduce dosage preparation time and the potential for prescribing and dispensing errors.

Mechanistic models for myelosuppression

As myelosuppression is the dose-limiting toxicity for most chemotherapeutic drugs, modelers attempt to find relationships between drug and toxicity to optimize treatment. Mechanistic models, i.e. models based on physiology and pharmacology, are preferable over empirical models, as prior information can be utilized and as they generally are more reliable for extrapolations. To account for different dosing-regimens and possible schedule-dependent effects, the whole concentration-time profile should be used as input into the pharmacokinetic-pharmacodynamic model. It is also of importance to model the whole time course of myelosuppression to be able to predict both the degree and duration of toxicity as well as consecutive courses of therapy. A handful of (semi)-mechanistic pharmacokinetic-pharmacodynamic models with the above properties have been developed and are reviewed. Ideally, a model of myelosuppression should separate drug-specific parameters from system related parameters to be applicable across drugs and useful under different clinical settings. Introduction of mechanistic models of myelosuppression in the design and evaluation of clinical trials can guide in the decision of optimal sampling times, contribute to knowledge of optimal doses and treatment regimens at an earlier time point and identify sub-groups of patients at a high risk of myelosuppression.

Epirubicin in patients with liver dysfunction: development and evaluation of a novel dose modification scheme

This study aimed to develop an epirubicin dose modification scheme in women with breast cancer and liver dysfunction. We first identified target areas under the concentration-time curve (AUCs) of 2400 and 1600 ng/ml.h from pharmacokinetic studies in 15 women with normal liver tests. In a second group of 16 women with abnormal liver biochemistry, the relationship between raised asparate aminotransferase (AST) and epirubicin clearance was: dose=AUC (97.5-34.2xlog AST). Adaptive dosing was evaluated prospectively in a third group of 41 women with serum AST > or =2xnormal+/-raised bilirubin. The median AUCs were 2444 and 1608 ng/ml.h, close to the high and low target AUCs, respectively. Variability in AUC was lower with adaptive dosing than in a fourth group given an unadjusted dose of epirubicin (coefficient of variation=25.8, 30.0 and 46.5%, respectively; P=0.06). Epirubicin dosing based on AST is safe and may reduce pharmacokinetic variability.

Pharmacokinetic-pharmacodynamic relationships of the anthracycline anticancer drugs

The anthracycline glycoside antibiotics represent a group of potent anticancer agents with a wide spectrum of activity against solid tumours and haematological malignancies, and are the mainstay of a large number of clinical protocols for the treatment of adult and childhood neoplastic diseases. Their clinical activity is limited, however, by acute and chronic adverse effects. Myelosuppression, predominantly neutropenia and leucopenia, is the dose-limiting toxicity; in addition to this, mucositis, nausea, vomiting and alopecia are frequent, whereas hepatopathy, characterised by elevated bilirubin concentrations, occurs less frequently. Cardiotoxicity is a major adverse effect of the anthracycline antibiotics and can be acute or chronic; in the acute setting, electrocardiographic abnormalities may be seen, including ST-T elevations and arrhythmias, but chronic cardiotoxicity represents a serious adverse effect that may be lethal due to the development of irreversible, cumulative dose-dependent, congestive cardiomyopathy. The occurrence of toxicity displays a marked interindividual variation, and for this reason the pharmacokinetics and pharmacodynamics of anthracyclines have been extensively investigated in order to identify integrated models that can be used in the clinical setting to prevent the development of serious toxicity, mainly leucopenia, and maximise tumour exposure. Pharmacokinetics has been recognised to influence both the toxicity and the activity of anthracyclines; in particular, there is increasing evidence that the mode of administration plays an important role for cumulative cardiotoxicity and data indicate that bolus administration, rather than continuous infusion, appears to be an important risk factor for anthracycline-induced cardiomyopathy, thus implying that this type of toxicity is maximum concentration-dependent. On the contrary, exposure to the drug, as measured by area under the curve, seems best related to the occurrence of leucopenia. Finally, the development of pharmacokinetic-pharmacodynamic models allows the simulation of drug effects and ultimately dose optimisation in order to anticipate important toxicities and prevent their occurrence by the administration of prophylactic treatments.

Pharmacokinetically guided administration of chemotherapeutic agents

The current practice for the dose calculation of most anticancer agents is based on body surface area in m2, although lower interpatient variation in pharmacokinetic parameters has been reported with pharmacokinetically guided administration. As chemotherapeutic agents have a narrow therapeutic window, pharmacokinetically guided administration may lead to less toxicity and higher efficacy than administration on the basis of body surface area. Pharmacokinetically guided administration, using parameters such as area under the plasma concentration-time curve (AUC), steady-state plasma drug concentration and drug exposure time above a certain plasma concentration, has been studied for many antineoplastic agents. Assessment of pharmacokinetic profiles allows the characterisation of relationships between pharmacokinetic parameters and efficacy and toxicity. AUC appears to be more closely correlated with pharmacodynamics than does the dose per unit of body surface area. In particular, the AUC-guided administration of carboplatin has been extensively studied, based on the close relationship between the renal clearance of the drug and glomerular filtration rate. Several formulae and limited sampling models have been derived to predict the AUC of carboplatin. The relationship between AUC and pharmacodynamics has also been studied for other anticancer agents, for example fluorouracil, topotecan, etoposide, cisplatin and busulfan, but all less extensively than for carboplatin. The pharmacokinetically guided administration of these agents needs to be investigated further before the use of alternative administration formulae can become standard clinical practice. Prospective studies of pharmacokinetically guided versus surface area-based administration should be performed to validate pharmacokinetic-pharmacodynamic relationships and to facilitate optimal dosage of anticancer agents in the clinic.

Sequence effect of epirubicin and paclitaxel treatment on pharmacokinetics and toxicity

PURPOSE

Sequence-dependent clinical and pharmacokinetic interactions between paclitaxel and doxorubicin have been reported. Some data have shown an influence of paclitaxel on epirubicin metabolism, but no data are available about the effect of diverse sequences of these drugs. We investigated whether reversing the sequence of epirubicin and paclitaxel affects the pattern or degree of toxicity and pharmacokinetics.

PATIENTS AND METHODS

Patients receiving epirubicin 90 mg/m(2) by intravenous bolus followed by paclitaxel 175 mg/m(2) over 3-hour infusion or the opposite sequence every 3 weeks for four cycles were eligible. Toxicity was recorded at nadir. Pharmacokinetic data were evaluated at the first and the second cycle and were correlated with toxicity parameters.

RESULTS

Thirty-nine consecutive stage II breast cancer patients were treated. Twenty-one patients received epirubicin followed by paclitaxel (ET group), and 18 received the opposite sequence (TE group). No significant difference in nonhematologic toxicity was seen. A lower neutrophil and platelet nadir and a statistically significant slower neutrophil recovery was observed in the TE group. Area under the concentration-time curve (AUC) of epirubicin was higher in the TE group (2,346 ng/mL. h v 1,717 ng/mL. h; P =.002). An inverse linear correlation between epirubicin AUC and neutrophil recovery was also observed (P =.012). No difference was detected in paclitaxel pharmacokinetics.

CONCLUSION

Our results support a sequence-dependent effect of paclitaxel over epirubicin pharmacokinetics that is associated with increased myelotoxicity. Because schedule modifications of anthracyclines and paclitaxel can have clinical consequences, the classical way of administration (ie, anthracyclines followed by paclitaxel) should be maintained in clinical practice.

A prolonged methoxymorpholino doxorubicin (PNU-152243 or MMRDX) infusion schedule in patients with solid tumours: a phase 1 and pharmacokinetic study

The aim of this phase I study was to assess feasibility, pharmacokinetics and toxicity of methoxymorpholino doxorubicin (MMRDX or PNU-152243) administered as a 3 h intravenous infusion once every 4 weeks. Fourteen patients with intrinsically anthracycline-resistant tumours received 37 cycles of MMRDX. The first cohort of patients was treated with 1 mg m(-2) of MMRDX. The next cohorts received 1.25 mg m(-2) and 1.5 mg m(-2) respectively. Common toxicity criteria (CTC) grade III/IV nausea and vomiting were observed in 1/18 cycles at 1.25 mg m(-2) and in 2/11 cycles at 1.5 mg m(-2). Transient elevation in transaminases up to CTC grade III was observed in 2/16 cycles at 1.25 mg m(-2) and 4/11 cycles at 1.5 mg m(-2). No cardiotoxicity was observed. At 1.25 mg m(-2) CTC grade IV neutropenia occurred in 1/17 cycles. At 1.5 mg m(-2) CTC grade III neutropenia was seen in 2/7 and grade IV in 3/7 evaluable cycles. Thrombocytopenia grade III was observed in 2/9 and grade IV in 1/9 evaluable cycles. One patient treated at 1.5 mg m(-2) died with neutropenic fever. Therefore, dose-limiting toxicity was reached and 1.25 mg m(-2) was considered the maximum tolerated dose for MMRDX as 3 h infusion. No tumour responses were observed. Pharmacokinetic parameters showed a rapid clearance of MMRDX from the circulation by an extensive tissue distribution. Renal excretion of the drug and its metabolite was negligible. In conclusion, prolongation of MMRDX infusion to 3 h does not improve the toxicity profile as compared with bolus administration.

Anthracyclines in haematology: pharmacokinetics and clinical studies

The activity of anthracyclines in the treatment of a wide spectrum of haematological malignancies has long been established. Differences in the pharmacokinetic and pharmacodynamic properties of these drugs have resulted in the selection of individual compounds for particular indications while the recent reformulation of anthracyclines in liposomal preparations seems likely to significantly alter their range of activity and toxicity. The problems related to cumulative cardiotoxicity secondary to anthracycline exposure can be ameliorated by the use of dexrazoxane and a number of agents may prove to have a role in altering their cellular resistance to their cytotoxic actions.

A general model for time-dissociated pharmacokinetic-pharmacodynamic relationship exemplified by paclitaxel myelosuppression

BACKGROUND

Hematologic toxicity after cancer chemotherapy and other drug effects that occur late compared to the exposure are usually modeled with use of some summary exposure variable such as the area under the concentration-time curve (AUC model) or the time of exposure above a threshold concentration (threshold model). An underlying assumption for both of these models is that the drug exerts a direct effect while present in the body and that it is the time integral of this direct effect that is related to the ultimate observed effect, either linearly (AUC model) or by a step function (threshold model). We propose a more general model that allows this relationship to be characterized by a nonlinear continuous function.

METHODS

Data on survival fraction of neutrophiles and time course of leukopenia from 92 courses of paclitaxel therapy in 21 patients with breast or ovarian cancer was related to paclitaxel concentration-time profiles with the AUC, threshold, and general models. The properties of the general model were also investigated with use of simulations.

RESULTS

For both pharmacodynamic end points, the general model described the data significantly better than the AUC or threshold models.

CONCLUSION

The general model is an extension to the present way of relating concentration-time profiles to late-effect measures, and it may provide an improved description of the concentration-response relationship and more accurate predictions of the ultimate effect when doses and schedules are varied. It can explain complex relationships between concentration-time profiles and the observed effect, and predictions from it lack some of the counterintuitive properties that the AUC or threshold model have when extrapolations are made.

Pharmacokinetics of anticancer agents in patients with impaired liver function

This report reviews published information on the clinical pharmacokinetics of antitumour agents in patients with liver dysfunction, associated with primary liver disease or liver metastases. Information was available for anthracyclines and their related compounds, antimetabolites, cyclophosphamide, vinca alkaloids, taxanes and epipodophyllotoxins. Changes in the pharmacokinetic profile or metabolism in patients with mild or severe hepatobiliary dysfunction are described and the relationships between serum levels, parameters employed for measuring hepatic function and toxic or therapeutic effects are examined. Current knowledge of the pharmacokinetics of antineoplastic agents in liver disease is far from complete, mostly obtained in small numbers of non-homogeneous patients often presenting only moderate liver dysfunction, and empirical guidelines for dose assessment are still largely applied in clinical practice. Because of the complex pathophysiological mechanisms of liver insufficiency in cancer patients, there is still doubt whether endogenous markers are useful. Although caution in treating cancer patients with liver insufficiency is compulsory, for most compounds there seems no need to recommend dose reductions for moderate impairment. However, for the tubulin acting agents, vincristine, vinblastine and possibly for paclitaxel and docetaxel, there is strong evidence that dose adjustment is mandatory in order to avoid excessive neutropenia and neurotoxicity.

Broad phase II and pharmacokinetic study of methoxy-morpholino doxorubicin (FCE 23762-MMRDX) in non-small-cell lung cancer, renal cancer and other solid tumour patients

The aim was to perform a broad phase II and pharmacokinetic study of methoxymorpholino-doxorubicin (MMRDX), a drug active against multidrug-resistant tumour cells in vitro when given by i.v. bolus at 1.5 mg m(-2) every 4 weeks, in metastatic or unresectable solid tumour patients with known intrinsic drug resistance. Patients received a maximum of six cycles. Plasma, urine and leucocyte MMRDX and its 13-dihydro metabolite pharmacokinetic analysis was performed in patients without liver metastases. Patients (n = 48, 21 NSCLC, 19 renal cell, three head and neck tumour, three cervical cancer and two adenocarcinoma of unknown primary) received 132 cycles of MMRDX. Common toxicity criteria (CTC) grade III/IV thrombocytopenia (12% of cycles) and neutropenia (27% of cycles) occurred with median nadir on day 22. Transient transaminases elevation > grade III/IV was observed in 7% of cycles, late and prolonged nausea > or = grade II in 34% and vomiting > or = grade II in 39%. In two patients, the left ventricular ejection fraction was reduced > or = 15%. Of 37 evaluable patients, one out of 17 NSCLC had a partial response. Mean (+/- s.d.) MMRDX AUC0-infinity calculated up to 24 h after dosing was 20.4 +/- 6.2 microg h l(-1) (n = 11) and t(1/2, gamma) was 44.2 h. Mean plasma clearance (+/- s.d.) was 37.2 +/- 7.3 l h(-1) m(-2) and volume of distribution 1982 +/- 64 l m(-2). MMRDX leucocyte levels 2 and 24 h after infusion were 450 to 600-fold higher than corresponding MMRDX plasma levels. In urine, 2% of the MMRDX dose was excreted unchanged, and 2% as metabolite. The main side-effects of 1.5 mg m(-2) every 4 weeks of MMRDX are delayed nausea and vomiting and haematological toxicity. MMRDX is characterized by extensive clearance and rapid and extensive distribution into tissues. A low response rate was observed in patients with tumours with intrinsic chemotherapy resistance.

Benefits of pharmacological knowledge in the design and monitoring of cancer chemotherapy

Prescribing chemotherapy is a difficult task, because of drug resistance, which prevents all tumors to respond to a given protocol and because of drug toxicity, which is generally unavoidable but which must be limited to acceptable levels. The therapeutic window of anticancer drugs is very narrow and clinicians have to try to optimize the individual doses and schedules of the drugs to be administered. They can rely upon simple anthropometric features, such as body weight or surface area; they can also take into account the physiological status of the patient: age, liver and kidney function, genetic characteristics of drug metabolism, etc. The best way for dose adaptation lies in the establishment of pharmacokinetic/pharmacodynamic relationships, i.e., between the behavior of a drug in the body and its efficacy and toxicity. When it is established that the optimal effect of a drug is related to a given parameter, such as the area under the curve plotting plasma concentration vs. time (AUC), it becomes possible to administer the drug with the dose allowing to obtain the target parameter value. Individual dose adaptation can be achieved thanks to the study of the pharmacokinetics of a test dose preceding that of the therapeutic dose, or by the measure of drug plasma levels, either at steady state during a protracted infusion, or from cycle to cycle during repetitive protocols. Population analysis now allows the adaptation of anticancer drug dosing from a minimum knowledge of individual pharmacokinetic features, together with other characteristics of the patients such as age, gender or physiological functions.

Phase I dose intensification study of 2-weekly epirubicin with GM-CSF in advanced cancer

This study investigated dose intensification of epirubicin administered as a 2-weekly regimen with granulocyte-macrophage colony-stimulating factor (GM-CSF) support. The aim was to define the maximally tolerated dose of epirubicin and to assess the efficacy of GM-CSF to ameliorate its toxicity. Patients with anthracycline-responsive advanced malignancies were eligible. Six dose levels, commencing at 90 mg/m2, of epirubicin administered every 2 weeks for four courses were planned with GM-CSF 10 micrograms/kg/day administered for 10 days from the second day of each course. Six patients were to be entered at each dose level, and escalation to the next level was based upon toxicity criteria. Twelve patients were entered, six at dose level 1 (90 mg/m2) and six at dose level 2 (120 mg/m2). Prospectively defined haematological dose-limiting toxicities were noted in one patient at dose level 1 and in five patients at dose level 2. Further dose escalation was not attempted. Significant nonhaematological toxicities included febrile neutropenia in two and four patients at dose levels 1 and 2, respectively. This study has demonstrated that epirubicin can be safely administered at 2 week intervals with GM-CSF at a dose of 90 mg/m2, equivalent to the previously reported maximum tolerated dose intensity of 45 mg/m2/week. Neutropenia was dose-limiting despite the use of GM-CSF.

High-dose epirubicin and r-met-hu G-CSF (filgrastim) in the treatment of patients with advanced breast cancer: A Hellenic Cooperative Oncology Group study

The delivery of high-dose epirubicin in patients with advanced breast cancer usually entails serious myelotoxicity and frequent treatment delays. Concurrent administration of G-CSF probably allows the administration of epirubicin on schedule with minimal morbidity. From August 1990 to February 1992, 42 women with advanced breast cancer were treated with six cycles of epirubicin 110 mg/m2 every 4 weeks. Filgrastim 5 micrograms/kg per day for 14 days was administered subcutaneously starting 24 hours after chemotherapy. All patients had multiple metastatic sites, and 39 had visceral metastases. All cases were evaluable for response, toxicity, and survival. Treatment was delayed in only two cases. The actually administered average dose per unit time per patient amounted to 99.6% of the dose prescribed by the protocol. Two (4.5%; 95% confidence interval [C.I.] 0-16%) patients demonstrated a complete response and 14 (33%; 95% C.I. 19-49%) a partial response. Median time to progression was 31 weeks and median survival was 60 weeks. Severe granulocytopenia was seen in six patients; stomatitis and diarrhea in one patient each. Myoskeletal pain was noticed in 23 (55%) patients, while cardiac problems were reported in 3 cases. The present study shows that the prophylactic use of r-met-hu G-CSF allows the administration of high-dose epirubicin every 4 weeks with minimal morbidity and an improved quality of life.

Individual dose adaptation of anticancer drugs

The dose of anticancer drugs is currently adjusted to the patient body surface area, although patients have different abilities to clear anticancer drugs. The dose adjustment to physiological functions permits major toxic accidents to be avoided. The adjustment to tumour drug content is considered, but for ethical or technical reasons, it cannot be used routinely The best criterion for the dose adjustment seems to be drug plasma concentration. The relationship between plasma concentration and efficacy may not be excellent, since it depends on the presence of resistant cells and on the blood flow through the tumour. A relationship between plasma concentration and/or the area under the curve (AUC) with toxicity has been reported with all major anticancer drugs. Different methods of dose adjustment to the drug plasma concentration are reported. In conclusion, dose adjustment to the drug plasma concentration or to the AUC can improve the chemotherapy efficacy, while reducing toxicity.

Epirubicin in hepatocellular carcinoma: pharmacokinetics and clinical activity

The pharmacokinetics and clinical activity of epirubicin were investigated in 16 patients with hepatocellular carcinoma (HCC) who received epirubicin at 75 mg/m2; the drug was given intravenously to 7 patients and via the hepatic artery to 9 patients (7 of whom also underwent embolisation). Lignocaine (1 mg/kg) was also given intravenously to 15 patients, and the metabolite monoethylglycinexylidide (MEGX) was measured as an indicator of liver function. Epirubicin clearance correlated with serum aspartate aminotransferase (AST), albumin and bilirubin values in patients treated intravenously or intraarterially. Although the route of administration did not affect the median total plasma clearance of epirubicin, early- and intermediate-phase clearance was higher following intraarterial administration. MEGX levels correlated with serum bilirubin levels but there was no correlation with albumin or AST values or epirubicin clearance. The rate of response to epirubicin was 3/13 (23%; 95% confidence interval, 8%-50%). Intravenous epirubicin was tolerated well, but intraarterial treatment was associated with significant morbidity. These data confirm that although current recommended dose adjustments are based primarily on serum bilirubin levels, altered epirubicin pharmacokinetics correlate more strongly with AST and albumin values than with serum bilirubin concentrations. However, at this dose and schedule, epirubicin has only modest activity against HCC.

Epirubicin. Clinical pharmacology and dose-effect relationship

The pharmacokinetic properties of epirubicin are characterised by a triphasic plasma clearance, with half-lives for the initial (alpha), intermediate (beta) and terminal (gamma) elimination phases of approximately 3 minutes, 1 hour and 30 hours, respectively. These values are similar to or slightly shorter than the corresponding half-lives of doxorubicin. The total plasma clearance of epirubicin is approximately 50 L/h/m2, which is almost 2-fold higher than that of doxorubicin. This difference is mainly due to the relatively high volume of distribution of epirubicin, and the unique glucuronidation metabolic pathway of epirubicin and epirubicinol, which is not available to doxorubicin or doxorubicinol. Glucuronide metabolites of epirubicin and epirubicinol are not active per se, but could divert epirubicin from free radical formation, which may induce cardiotoxic effects. This may explain, at least in part, the lower cardiotoxicity of this new anthracycline relative to that of the parent compound. There is a linear relationship between the dose administered and area under the plasma concentration-time curve (AUC) values of both unchanged drug and metabolites, so that the total plasma clearance of epirubicin is constant with epirubicin doses ranging from 40 to 140 mg/m2. No variation in total plasma clearance as a function of age in the range of 31 to 74 years has been observed, and this parameter is unaffected by subsequent courses of treatment. Hepatic dysfunction causes an increase in the terminal elimination half-life of epirubicin, which is well correlated with serum bilirubin levels and which necessitates a reduction in epirubicin dosage. Epirubicin is responsible for a dose-dependent neutropenia, which is clearly related to drug exposure as established in pharmacodynamic studies. The maximum tolerated dose (MTD) of epirubicin was first established to be approximately 90 mg/m2 but this was re-examined recently and is now deemed to be approximately 150 mg/m2, which is about 2-fold higher than the MTD of doxorubicin. Cumulative cardiac toxicity occurs for both epirubicin and doxorubicin, but the dose ratio for equal risk is about 1.8 in favour of epirubicin (500 to 550 mg/m2 for doxorubicin vs 900 to 1000 mg/m2 for epirubicin). Consequently, there is not a higher risk of developing cardiotoxicity after administration of high dose epirubicin, since this adverse effect is associated with total cumulative anthracycline dose. In several controlled trials, epirubicin exhibited the same anticancer activity as doxorubicin when administered at equimolar doses to patients with advanced breast cancer.(ABSTRACT TRUNCATED AT 400 WORDS)

Epirubicin as a single agent therapy for the treatment of breast cancer--a pharmacokinetic and clinical study

Sixty women with breast cancer (mean age: 61 years; range 36-78 years) were treated with Epirubicin (4'epi-Doxorubicin), 60 mg m-2, as single drug therapy. The drug was administered as 2 hours' constant rate infusions. The pharmacokinetics of the drug during the first course of treatment was evaluated by measurements of the plasma concentration of Epirubicin at the end of the infusion period. There was a five-fold inter-individual variation of the dose-normalized maximum plasma concentration, which increased with increasing age of the patients. There was no correlation between this pharmacokinetic parameter and degree of obesity. An increase in maximum plasma concentration was associated with an increasing degree of alopecia (p = 0.025). Also the degree of nausea and vomiting showed a tendency to increase with increasing maximum plasma concentration (p = 0.07). Fifty four of the sixty patients entered in the present study were evaluable for clinical response. There was one CR (complete remission). Seventeen patients achieved PR (partial response), and twenty five patients had SD (stable disease). Eleven patients did not respond to treatment. The median maximum plasma concentrations were 322, 316, 336 and 288 ng ml-1 in patients with CR, PR, SD and PD, respectively. The results in the present study showed that 60 mg m-2 of Epirubicin given as a constant rate infusion over 2 hours is a useful alternative to more aggressive combination drug therapy for the treatment of breast cancer.

Influence of the cardioprotective agent dexrazoxane on doxorubicin pharmacokinetics in the dog

The influence of dexrazoxane on doxorubicin pharmacokinetics was investigated in four dogs using the two treatment sequences of saline/doxorubicin or dexrazoxane/doxorubicin. Intravenous doses of 1.5 mg/kg doxorubicin and 30 mg/kg (the 20-fold multiple) dexrazoxane were given separately, with doxorubicin being injected within 1 min of the dexrazoxane dose. Both doxorubicin and its 13-dihydro metabolite doxorubicinol were quantified in plasma and urine using a validated high-performance liquid chromatographic (HPLC) fluorescence assay. The doxorubicin plasma concentration versus time data were adequately fit by a three-compartment model. The mean half-lives calculated for the fast and slow distributive and terminal elimination phases in the saline/doxorubicin group were 3.0 +/- 0.5 and 32.2 +/- 12.8 min and 30.0 +/- 4.0 h, respectively. The model-predicted plasma concentrations were virtually identical for the saline and dexrazoxane treatment groups. Analysis of variance of the area under the plasma concentration-time curve (AUCo-infinity), terminal elimination rate (lambda z), systemic clearance (CLs), and renal clearance (CLr) for the parent drug showed no statistically significant difference (P greater than 0.05) between the two treatments. Furthermore, the doxorubicinol plasma AUCo-t value and the doxorubicinol-to-doxorubicin AUCo-t ratio showed no significant difference, demonstrating that dexrazoxane had no effect on the metabolic capacity for formation of the 13-dihydro metabolite. The total urinary excretion measured as parent drug plus doxorubicinol and the metabolite-to-parent ratio in urine were also unaffected by the presence of dexrazoxane. The myelosuppressive effects of doxorubicin as determined by WBC monitoring revealed no apparent difference between the two treatments. In conclusion, these results show that drug exposure was similar for the two treatment arms. No kinetic interaction with dexrazoxane suggests that its coadministration is unlikely to modify the safety and/or efficacy of doxorubicin.