Population pharmacokinetics of docetaxel during phase I studies using nonlinear mixed-effect modeling and nonparametric maximum-likelihood estimation

Docetaxel, a novel anticancer agent, was given to 26 patients by short i.v. infusion (1–2 h) at various dose levels (70–115 mg/m², the maximum tolerated dose) during 2 phase I studies. Two population analyses, one using NONMEM (nonlinear mixed-effect modeling) and the other using NPML (nonparametric maximum-likelihood), were performed sequentially to determine the structural model; estimate the mean population parameters, including clearance (Cl) and interindividual variability; and find influences of demographic covariates on them. Nine covariates were included in the analyses: age, height, weight, body surface area, sex, performance status, presence of liver metastasis, dose level, and type of formulation. A three-compartment model gave the best fit to the data, and the final NONMEM regression model for Cl wasCl=BSA(1+2×AGE), expressing Cl (in liters per hour) directly as a function of body surface area. Only these two covariates were considered in the NPML analysis to confirm the results found by NONMEM. Using NONMEM [for a patient with mean AGE (52.3 years) and mean BSA (1.68 m²)] and NPML, docetaxel Cl was estimated to be 35.6 l/h (21.2 lh^–1 m^–2) and 37.2 l/h with interpatient coefficients of variation (CVs) of 17.4% and 24.8%, respectively. The intraindividual CV was estimated at 23.8% by NONMEM; the corresponding variability was fixed in NPML in an additive Gaussian variance error model with a 20% CV. Discrepancies were found in the mean volume at steady state (Vss; 83.2 l for NPML versus 124 l for NONMEM) and in terminal half-lives, notably the meant _1/2, which was shorter as determined by NPML (7.89 versus 12.2 h), although the interindividual CV was 89.1% and 62.7% for Vss andt _1/2, respectively. However, the NPML-estimated probability density function (pdf) oft _1/2, was bimodal (5 and 11.4 h), probably due to the imbalance of the data. Both analyses suggest a similar magnitude of mean Cl decrease with small BSA and advanced age.     

A phase I study of 9-aminocamptothecin as a colloidal dispersion formulation given as a fortnightly 72-h infusion

Purpose A phase I pharmacologic study was undertaken to determine the maximum tolerated dose (MTD), to characterize the pharmacokinetic profile, and to evaluate all toxicities of the aqueous colloidal dispersion formulation of 9-aminocampothecin (9-AC).Methods 9-AC was administered as a constant 72-h i.v. infusion every 2 weeks to adult cancer patients at dose rates ranging from 25 to 59 g/m² per hour.Results Twenty patients with refractory solid tumors received a total of 86 courses of 9-AC at four dose levels. Myelosuppression, particularly granulocytopenia, was the most common toxicity. Two of six assessable patients entered at 59 g/m² per hour had dose-limiting toxicity (grade 3 diarrhea or need for a 2-week treatment delay to permit granulocyte recovery), whereas lower doses were well tolerated. At the recommended dose, 47 g/m² per hour, the average steady-state plasma levels (Cpss) and area under the curve (AUC) of 9-AC lactone and total drug were 15 and 75 nM, and 1034 and 4220 nM·h, respectively. A moderate correlation was seen between 9-AC lactone AUC and the percentage decrease in granulocytes.Conclusions The recommended phase II dose of 9-AC colloidal dispersion as a 72-h infusion every 14 days is 47 g/m² per hour (1.13 mg/m² per day). The Cpss of 9-AC lactone at this dose exceeded the 10 nM threshold level for preclinical activity.     

The pharmacokinetics of a 1-h paclitaxel infusion

Purpose: To characterize the disposition of paclitaxel (PAC) after a 1-h infusion in humans and define if possible a pharmacodynamic relationship between PAC disposition and the observed toxicity. Patients and methods: PAC pharmacokinetics were studied in 43 courses of therapy in 30 patients (30 first course, 13 PK third course). PAC was administered at 150, 175, 200, 225 and 250 mg/m² by a 1-h infusion to patients with advanced cancer (lung, breast, ovarian, cervix, and head and neck). PAC was quantified by high-performance liquid chromatography (HPLC). Pharmacokinetic parameters were calculated by noncompartmental and model-dependent methods. Results: Increases in the area under the curve and the peak plasma concentration were not proportional to increases in the dose. However, the deviation from linearity is rather moderate. The dose-limiting toxicity was central neuropathy which was not associated with pharmacokinetic deviations. Owing to the absence of grade 3 or 4 myelotoxicity, no clear correlation between this toxicity and pharmacokinetic parameters could be established. Conclusion: Within the evaluated dose range of the 1-h infusion there was only a moderate nonlinear disposition of PAC in humans and therefore a dose of 225 mg/m² is recommended as safe. The observation of central neuropathy could not be directly related to a pharmacokinetic parameter. The complexity of the formulation which included Cremophor EL and ethanol may offer an explanation for the observed central neurotoxicity. Received: 24 May 1999 / Accepted: 16 December 1999     

Phase I clinical and pharmacokinetic trial of docetaxel and irinotecan administered on a weekly schedule

Background Docetaxel and irinotecan are synergistic agents with a broad spectrum of activity but overlapping myelosuppression. The study was designed to maintain dose intensity while limiting myelosuppression. The objectives of this study were to determine the maximal tolerated dose (MTD) of the combination of docetaxel and irinotecan administered weekly for four consecutive weeks every 42 days, to describe toxicities of this regimen, and to perform a pharmacokinetic analysis to evaluate changes in drug disposition as a function of dose as well as repeated dosing.Methods Adult patients with advanced solid tumors were treated with docetaxel followed by irinotecan. Doses of 30/50, 35/50, 35/66, 30/57, 30/65, 30/80 mg/m², respectively, were studied. Pharmacokinetics of docetaxel, irinotecan and SN-38 in plasma were determined on days 1 and 22 by a high-performance liquid chromatography (HPLC) assay.Results A total of 35 patients were treated. The MTD was docetaxel 30 mg/m² plus irinotecan 65 mg/m². Diarrhea was the dose-limiting toxicity; myelosuppression and other non-hematological toxicities were uncommon and mild. There were no significant differences in pharmacokinetic parameters between day 1 and day 22 (n=20). Five objective responses (breast, stomach and unknown primary) were observed among 30 evaluable patients. In addition, eight patients achieved stable disease.Conclusions The combination of weekly docetaxel and irinotecan is a well tolerated regimen and should be explored in phase II trials. This schedule maintains dose intensity and has limited myelosuppression.     

Pharmacokinetics of decitabine administered as a 3-h infusion to patients with acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS)

Purpose In this study, pharmacokinetics (PK) of decitabine administered as a 3-h intravenous infusion of 15 mg/m² every 8 h for 3 days (cycles repeated every 6 weeks) was evaluated in patients with MDS or AML. Methods The PK of this dosing regimen was evaluated in sixteen patients with MDS or AML. Plasma samples were obtained pre-dose and during the first 8-h dosing interval on each dosing day during Cycle 1, and at pre-dose and just prior to the end of infusion during Cycle 2. PK samples were assayed for decitabine by a sensitive and specific validated liquid chromatography-tandem mass spectrometry method. Results The mean maximum observed plasma concentration (C _max), 64.8–77.0 ng/ml, and the mean area under the plasma concentration-time curve (AUC_0-∞), 152–163 ng h/ml, were unchanged during dosing of decitabine for 3 days. The time to the maximum concentration (T _max) generally occurred at the end of infusion. The mean values for terminal phase elimination half-life (0.62–0.78 h), total body clearance (125–132 l/h per m²), and volume of distribution at steady state (62.7–89.2 l/m²), remained unchanged during the every 8 h dosing (P > 0.05). Cycles 1 and 2 C _max values for days 1, 2, and 3 were not significantly different as determined by paired two-tailed t test (P > 0.05). The primary toxicity of decitabine was myelosuppression, which was observed in all patients. Two deaths, from sepsis, were considered possibly related to decitabine. Conclusions Decitabine dosed at 15 mg/m² iv every 8 h for 3 days resulted in a predictable and manageable toxicity profile in patients with MDS/AML. The repeated dosing did not result in systemic accumulation of the drug, and decitabine PK remained unchanged from cycle to cycle.     

Pharmacokinetics and pharmacodynamics of topotecan administered daily for 5 days every 3 weeks

Topotecan is a novel semisynthetic derivative of the anticancer agent camptothecin and inhibits the intranuclear enzyme topoisomerase I. The lactone structure of topotecan, which is in equilibrium with the inactive ringopened hydroxy acid, is essential for this activity. The open form predominates at physiological pH. We performed a pharmacokinetic, study as part of a phase I study in patients with various types of solid tumors, where topotecan was administered in a 30-min infusion daily on 5 consecutive days every 3 weeks. The plasma kinetics of topotecan could be described best using an open two-compartment model with t1/2() and t1/2() of 8.1 (range 0.3 to 40.7) min and 132 (range 49 to 286) min, respectively. The plasma concentration-time profiles of the metabolite, however, could be described using a one-compartment model with t1/2(formation) of 29.0 (range 5.6–99.5) min and t1/2 (elimination of 123.2 (range 32–265) min, respectively. The lactone was the predominate form during the first hour from the start of infusion, but was rapidly converted into its ring-opened structure. The elimination rate of topotecan was independent of the dose. There were linear relationships between the dose (mg m^–2 day^–1), the area under the plasma concentration versus time curve (AUC) of topotecan and its metabolite, the total AUC, peak plasma lactone concentrations, and the time period that the topotecan concentrations remained above 10 nM. Different models were used to correlate pharmacokinetic and pharmacodynamic parameters. The percentage decrease in absolute neutrophil count (ANC) was related to these parameters and plots were well fitted by linear and sigmoidal E_max models.     

Pharmacokinetics and metabolism of doxorubicin after short-term infusions in lymphoma patients

Purpose/Methods: Twenty-four patients (17 males and 7 females with a mean age of 54 years) with malignant lymphoma participated in a study of doxorubicin pharmacokinetics after 50 mg/m² as 10-min infusions. In addition to plasma samples, serial leukocyte samples and – in one subject – serial biopsy specimens from lymphoma infiltrates were obtained. The samples were analysed by reversed-phase high-performance liquid chromatography. Results: In contrast to several previous studies, the data suggested that 7-deoxydoxorubicinolone, and not doxorubicinone, is a metabolite of doxorubicin in humans. Doxorubicin, but no metabolites, was present in significant and fairly constant concentrations in circulating leukocytes. These levels may reflect the drug levels in lymphoma infiltrates. The data further suggest that metabolism to 7-deoxydoxorubicinone is subject to large interindividual variation, possibly due to a genetic polymorphism, and that significant levels of a metabolic product which may be a doxorubicin glucuronide can be recovered from plasma of patients treated with doxorubicin. Received: 30 November 1998 / Accepted: 16 March 1999     

Pharmacokinetics and metabolism of pirarubicin in humans: correlation with pharmacodynamics

The pharmacokinetic monitoring of anthracycline-containing regimens is warranted because of the important toxicity of these drugs and because pharmacokinetic-pharmacodynamic relationships have been clearly established. We studied the pharmacokinetics of the new anthracycline pirarubicin in 80 courses of treatment performed in 27 patients, using a limited sampling protocol we had previously validated. We observed (for 47 of these courses) a significant correlation between the leucocyte cell kill and the pirarubicin area under the timexconcentration curve, but the most significant correlation was obtained using the plasma concentration of doxorubicin, a metabolite of pirarubicin, at the end of the infusion. On the basis of this value, it is possible to predict for pirarubicin haematological toxicity in a way that can help the clinician in identifying patients at risk for toxicity.     

Cyclophosphamide metabolism in children following a 1-h and a 24-h infusion

PURPOSE: The pharmacokinetics and metabolism of cyclophosphamide (CPA) when given as a 1-h and a 24-h infusion to children were compared. METHODS: Thirteen children with a variety of different malignancies received an identical dose of cyclophosphamide as a 1- and 24-h infusion. In each case the concentration of CPA and its principal metabolites were measured by a thin-layer-chromatography-photographic-densitometry technique. RESULTS: Cyclophosphamide clearance was greater during the 24-h infusion, following time-dependent increases in the metabolism of the drug (autoinduction) (median 5.1 vs 3.1 l/h/m2: P = 0.037). Autoinduction was seen in five children (38%), producing a median end of infusion concentration of 49% (range 28-89%) of the maximum and was not accompanied by an increase in the production of the principal inactive metabolites carboxyphosphamide and dechloroethylcyclophosphamide. CONCLUSIONS: These results suggest potential benefits of prolonging the infusion of CPA in clinical practice.     

Pharmacokinetics of once and twice daily dosing of intravenous tobramycin in paediatric patients with cystic fibrosis

The optimal dosing of intravenous tobramycin for treatment of pulmonary exacerbations in paediatric cystic fibrosis (CF) patients has not been completely delineated. We performed a retrospective study evaluating the pharmacokinetics and pharmacodynamics of once daily dosing (ODD) of IV tobramycin compared to twice daily dosing (TDD). Fifty-nine and 44 patients were included in the ODD and TDD groups, respectively. Once daily dosing achieved higher C_max as compared to TDD (29.5?±?11.0 vs 19.0?±?4.9, P?P?P?C_max:MIC for MICs >1.0?mg/l. Twice daily dosing may be a viable alternative to ODD in treating organisms with MICs ≤?1.0?mg/l; however, with MICs >1.0?mg/l, ODD is likely necessary to achieve goal C_max:MIC ratios.     

Pharmacokinetics and metabolism of epirubicin administered as i.v. bolus and 48-h infusion in patients with advanced soft-tissue sarcoma.

We have studied the pharmacokinetics of epirubicin after its administration in sarcoma patients either as an i.v. bolus or as a 48-h infusion (5 courses each; 9 patients in total). Bolus injection was followed by a three exponential decay in plasma, with half-lives of 2.43 min, 1.95 h and 21.7 h; 48-h infusions were characterized by the very rapid establishment of a plasma plateau concentration followed by a biexponential decay after stopping the infusion. Pharmacokinetic parameters such as total plasma clearance, total volume of distribution, mean residence time and elimination half-life were similar, irrespective of the duration of the administration. In contrast, the relative amounts of the metabolites of epirubicin were reduced when the drug was administered over 48 h; in particular, the plasma levels of epirubicin glucuronide never exceeded those of epirubicin, which always occur after bolus injection. This may result from a lower availability of epirubicin for metabolism. These results now require validation in a larger group of patients using a cross-over design.     

A phase I clinical and pharmacokinetic study of the dolastatin analogue cemadotin administered as a 5-day continuous intravenous infusion

Purpose: The dolastatins are a class of naturally occurring cytotoxic peptides which function by inhibiting microtubule assembly and tubulin polymerization. Cemadotin is a synthetic analogue of dolastatin 15 with potent antiproliferative and preclinical antitumor activity. This report describes a phase I study to evaluate the administration of cemadotin to adult cancer patients by a 5-day continuous intravenous (CIV) infusion. Methods: All patients had histologically confirmed refractory solid tumors. The dose was escalated from an initial level of 2.5 mg/m² (0.5 mg/m² daily) according to a modified Fibonacci algorithm. A minimum of three patients was evaluated at each dose level until the maximum tolerated dose (MTD) was established. Treatment was repeated every 21 days until patients were removed from the study due to toxicity or disease progression. Drug-related toxicities were evaluated and graded by the U.S. National Cancer Institute's Common Toxicity Criteria. A radioimmunoassay (RIA) that detected both the parent drug and its metabolites with an intact N-terminal region of the molecule was used for pharmacokinetic studies. Results: Twenty heavily pretreated patients received a total of 40 courses of cemadotin over five dose levels ranging from 2.5 to 17.5 mg/m². Reversible dose-related neutropenia was the principal dose-limiting toxicity and 12.5 mg/m² was established as the MTD. Nonhematologic toxicities attributed to the drug were moderate, and there was no evidence of the cardiovascular toxicity noted in the prior phase I studies of cemadotin given IV as a 5-min injection or 24-h infusion. There were no objective antitumor responses. Time courses of the cemadotin RIA equivalent concentration in whole blood were defined in 14 patients during the first cycle of therapy. The RIA-detectable species exhibited apparent first-order pharmacokinetics across the entire range of doses. The mean ± SD of the observed steady-state blood concentration at the 12.5 mg/m² MTD was 282 ± 7 nM (n=3). Blood levels decayed monoexponentially following the end of the infusion, with a mean half-life of 13.2 ± 4.3 h (n=14) in all patients. Mean values (n=14) of the total blood clearance and apparent volume of distribution at steady state were 0.52 ± 0.09 l/h/m² and 9.9 ± 3.3 l/m², respectively. Conclusions: The cardiotoxic effects of cemadotin were completely avoided by administering it as a 120-h CIV infusion. Thus, cardiovascular toxicity appears to be associated with the magnitude of the peak blood levels of the parent drug or its metabolites, whereas myelotoxicity is related to the duration of time that blood levels exceed a threshold concentration. Nevertheless, the data acquired during the extensive clinical experience with cemadotin requires careful examination to assess whether advancing this compound into disease-oriented efficacy studies is merited. Received: 8 November 1999 / Accepted: 28 April 2000     

高剂量表阿霉素在肿瘤患者中的药物动力学和药效学研究

目的：研究高剂量表阿霉素（ＥＰＩ）在肿瘤化疗患者体内的药物动力学过程,并初步探讨药效学特点。方法：１１例肿瘤患者接受了包含１００ｍｇ／ｍ＾２高剂量ＥＰＩ的联合化疗,高效液相色谱法（ＨＰＬＣ）测定血药浓度,ＰＬＮＯＮＬＩＮ程序进行药动力学房室模型数据拟合和参数计算;血液学毒性指标作为药效学参数,进行药动力学和药效学相关性及剂量调整因素的研究。结果：高剂量ＥＰＩ的消除具有典型的三室特征,患者对ＥＰＩ的     

Evaluation of the linearity of docetaxel pharmacokinetics

The taxanes, paclitaxel and docetaxel, have favorable response rates in patients with breast, gynecologic, and lung cancers and have demonstrated activity against a variety of malignancies. In human trials, paclitaxel pharmacokinetics are nonlinear and are best fit by a three-compartment model with nonlinear distribution into the second compartment as well as nonlinear elimination. This finding is important for patients receiving paclitaxel at high doses or as a short infusion, as it results in disproportionately high peak concentrations and delayed elimination. The presence of nonlinear processes in docetaxel pharmacokinetics has not previously been examined. Therefore, plasma concentration data obtained from 53 patients receiving docetaxel at 55–115 mg/m² over 1–24 h as part of phase I studies were modeled using the nonlinear three-compartment model found most suitable for paclitaxel and the results were compared with those obtained using the linear version. Docetaxel disposition was best described by the three-compartment nonlinear model in 28 of 53 data sets (53%). However, the difference in curve fit observed between the two models was modest (did not improve Akaike criteria) and unlikely to be of relevance. This study suggests that nonlinear processes in docetaxel pharmacokinetics may exist, but, unlike the case of paclitaxel, they are not likely to have a significant impact at the dose and administration schedule used in routine clinical practice (60–100 mg/m² given over 1 h by infusion). The presence of nonlinear docetaxel pharmacokinetics at doses above 115 mg/m² will have to be determined in case of further dose escalation. Received: 11 October 1997 / Accepted: 3 December 1997     

Methotrexate administered by 6-h and 24-h infusion: a pharmacokinetic comparison

Summary The pharmacokinetics of 8 g/m² methotrexate (MTX) was compared following short (6 h) and long (24 h) infusions of the drug to 11 children with osteogenic sarcoma (OS; 42 infusion) and 28 children with acute lymphoblastic leukemia (ALL: 118 infusions), respectively. No difference was observed in the first-phase half-life, in systemic clearance or in the volume of distribution of the drug (P>0.05). The concentration of MTX at the end of the infusion was 4-fold higher when the drug was given over only 6 h. However, patients receiving 24-h infusions had 9-fold higher levels by 24 h after the beginning of the infusion. The area under the data curve from start of the MTX infusion until the beginning of folinic acid rescue administration was significantly higher in patients with osteogenic sarcoma (6-h infusions), while the area under the log-data curve was significantly longer in the ALL group (24-h infusions) for the same period. The latter parameter is considered to be characteristic for the concentration-time-effect relationship. The longer duration of MTX administration (with delayed rescue) is thought to be more beneficial from the pharmacokinetic aspect. Patients with osteogenic sarcoma had significantly lower concentrations of MTX at the end of their last treatment with MTX than at the end of the first infusion. Patients developing MTX toxicity had shorter half-lives of MTX in the beta phase. It is suggested that cisplatin induced tubular loss of MTX and folinic acid is responsible for these observations. A wider application of clinical pharmacologic findings in the practice of the administration of cytostatics is indicated.The work reported in this paper was supported by a research grant from the Norwegian Cancer Society (Landsforeningen mot Kreft)     

Treatment of androgen-independent, hormone-refractory prostate cancer with docetaxel in Japanese patients

Background Although patients with prostate cancer with metastatic lesions initially respond to androgen ablation therapy, most patients ultimately develop a hormone-refractory state. Effective treatment for men with hormone-refractory prostate cancer (HRPC) has not been established. We performed a clinical study of docetaxel in HRPC patients, and evaluated its efficacy.Methods Nine patients with HRPC were administered 55 mg/m² docetaxel, every 3 weeks, simultaneously with hormonal therapy, with a luteinizing hormone-releasing hormone analog, and daily oral dexamethasone. Change in serum prostate-specific antigen (PSA) was determined as the primary endpoint.Results The mean age of the patients was 64 years (range, 49 to 76 years). Median follow-up time was 8.5 months (range, 5.3 to 16.7 months). In eight patients whose pretreatment serum PSA was elevated, six patients (75.0%) had a PSA decline of more than 50%, and four (50.0%) had a PSA decline of more than 75%. Median time to progression for all patients was 7.9 months (range, 0.0 to 11.6 months; 95% confidence interval [CI], 0.0 to 26.3). The median overall survival was 8.5 months (range, 5.3 to 16.7 months; 95% CI, 8.1 to 13.8). Four of six patients (66.7%) with pain before treatment obtained pain relief and were able to discontinue analgesic agents. This regimen was well tolerated. Grade 3 or 4 neutropenia or leukocytopenia without fever was seen in three patients (33.3%). Only one patient required administration of granulocyte-colony stimulating factor because of neutropenia. No other grade 3 or 4 toxicity was observed.Conclusion Docetaxel was an active agent in Japanese HRPC patients, and was well tolerated in this population. To establish its efficacy and safety in Japanese HRPC patients, a large-scale study in Japan is warranted.     

A phase I trial of gemcitabine administered as a 96-h continuous intravenous infusion in patients with advanced carcinoma and lymphoma

Background and objective Preclinical data suggest gemcitabine may have schedule-dependent activity fovoring prolonged infusion. We sought to determine the recommended phase II dose (RPTD) and toxicity of gemcitabine when given as a continuous intravenous (CIVI) over 96 h. Patients and methods Gemcitabine was initially given at 1 mg/m²/d for 48, then, 72, and finally 96 h. The dose was then increased to 2, 4, 6, 10, 15, 20, and 25 mg/m²/d. Dose levels of 7, 8, 9 mg/m²/d as 96-h infusion were added later after a protocol modification. After identifying the RPTD using an every 3-wk schedule. we then evaluated the feasibility of repeating the infusion every 2 wk, and then weekly for 3 of 4 wk. Results Thirty-four patients with a variety of tumor types received a total of 126 cycles of therapy (median of 2 cycles, range 1–10 cycles). The RPTD, was 8 mg/m²/d every 3 wk, and 6 mg/m²/d every 2 wk. The most common grade 2 or higher toxicities at all dose levels (>- grade 2) included fever (n=14), dyspnea (n=7). mucositis (n=6), hypotension (n=6), nausea/vomiting (n=6), and fatigue (n=5). Neutropeni and/or thrombocytopenia were uncommon. Conclusion A dministration of gemcitabine as a 96-h infusion results in a markedly different toxicity profile and RPTD than when given by a conventional 30-min infusion. The RPTD was 8 mg/m²/d (32 mg/m²/course) when given every 3 wk, or 6 mg/m²/d (24 mg/m²/course) when given every 2 wk.     

The pharmacokinetics of epirubicin and docetaxel in combination in rats

Purpose: The aim of the present study was to investigate possible pharmacokinetic interactions between epirubicin (EPI) and docetaxel (DTX) in rats. Methods: Male Sprague Dawley rats (n = 36) were used in the study. They received either DTX (5 mg/kg, n = 9), EPI (3.5 mg/kg, n = 13), or a combination (5 mg/kg + 3.5 mg/kg, n = 14), administered as intravenous bolus doses. Blood samples were collected at various time-points between 3 min and 45 h after dose administration. DTX and EPI plasma concentrations were determined by HPLC analysis. Pharmacokinetic evaluation was carried out using the NONMEM program. Results: A three-compartment model best described the concentration-time profiles for EPI. Clearance (CL), intercompartmental clearances (Q2 and Q3), central (V1) and peripheral (V2 and V3) volumes of distribution were estimated as 3.57 l/h per kg, 5.01 l/h per kg, 12.48 l/h per kg, 0.805 l/kg, 3.67 l/kg and 158 l/kg, respectively. A two-compartment model was sufficient to describe the DTX data. CL, intercompartmental clearance (Q), V1 and V2 for DTX were estimated as 7.3 l/h per kg, 4.6 l/h per kg, 0.69 l/kg and 2.6 l/kg, respectively. No significant change in the disposition of either drug was found when they were administered in combination compared to when they were given singly. Conclusion: Concurrent treatment with EPI and DTX does not appear to cause any changes in the pharmacokinetics of the drugs in rats. Received: 3 December 1998 / Accepted: 7 April 1999     

Pharmacokinetics of ecteinascidin 743 administered as a 24-h continuous intravenous infusion to adult patients with soft tissue sarcomas: associations with clinical characteristics,pathophysiological variables and toxicity

PURPOSE: Ecteinascidin 743 (ET-743) is a potent cytotoxic alkaloid of marine origin that has shown promising evidence of antitumor activity during phase I clinical trials. In the study reported here, the influence of clinical characteristics and pretreatment pathophysiological variables on the pharmacokinetics of ET-743 and their associations with drug-related toxicity was examined in sarcoma patients treated in three phase II clinical trials. METHODS: Adult patients with various histological subtypes of soft tissue sarcoma received 1.5 mg/m(2) of ET-743 by 24-h continuous i.v. infusion once every 3 weeks. Eligibility criteria were similar for each study, except for the histological subtype of the tumor or the extent of prior treatment with other anticancer agents, and all patients had normal or near-normal liver and renal function. The maximum plasma concentration (C(max)) and area under the plasma profile from time zero to infinity (AUC) of the drug were determined during the first cycle of therapy. Patients were evaluated for toxicity every week. RESULTS: Geometric mean +/- SD values of the pharmacokinetic parameters in 69 patients were: C(max) 1.14 +/- 0.52 ng/ml, AUC 39.9 +/- 16.6 ng.h/ml, and total body clearance (CL) 36.7 +/- 16.4 l/h per m(2). The only significant correlation involving physical characteristics of the patients or pretreatment pathophysiological variables was a very weak relationship between alkaline phosphatase and AUC (r=0.39, P<0.01). The 15 patients with any baseline liver function test exceeding the upper limit of the normal ranges had a significantly greater (P=0.02) incidence of severe toxicity (80% vs 44%). Although the mean AUC of ET-743 in patients with elevated serum levels of hepatic enzymes was 17% greater than that in patients with normal pretreatment liver function tests, the difference was not significant ( P=0.22). In addition, there was no distinct relationship between the grade of the most severe drug-related toxicity that occurred during the first cycle of therapy and the AUC for the entire cohort. The CL of ET-743 was found to be 27% greater in patients concurrently receiving dexamethasone as a preventative antiemetic than in those who were not, but the difference did not achieve statistical significance (P=0.08). There were no significant associations between CL (liters per hour) and body surface area or any other variable related to body size. CONCLUSIONS: The risk of developing severe toxicity was substantially enhanced in patients with relatively moderate indications of hepatic dysfunction without a coincident effect on the CL of ET-743. Dexamethasone cotreatment appeared to decrease the incidence of severe toxicity as well as the AUC of the drug. Delivering a fixed amount of drug without adjustment for the height or weight of the patient may be more appropriate than dose normalization due to the absence of an association between CL and body surface area. Optimizing dosing strategies to further enhance the therapeutic index of ET-743 may depend upon obtaining a better understanding of the metabolic fate of the drug in humans.     

多西紫杉醇脂质体的制备及其在家兔体内的药代动力学

背景与目的:多西紫杉醇(Docetaxel,DOC)已在临床应用于非小细胞肺癌、乳腺癌、卵巢癌等的治疗,但其水溶性差,现临床使用的注射剂均采用吐温-80和13%乙醇溶液作为混合溶媒,静脉注射时常引发严重的过敏反应而限制了其临床使用.本课题研究DOC脂质体的制备方法,并考察用聚乙二醇2000(poly ethylene glycol-2000,PEG-2000)修饰前后的两种脂质体在家兔体内的药代动力学.方法:用薄膜蒸发法制备普通和PEG-2000修饰的DOC脂质体,测定其包封率、粒径和表面电位;静脉注射给药后,以地西泮为内标,采用固相萃取-高效液相色谱法测定血浆中药物含量;用3p87程序和SPSS13.0统计软件处理和分析数据,计算有关药代动力学参数.结果:制备的DOC脂质体包封率＞75%,平均粒径在150 nm左右.普通市售多西紫杉醇注射液(market docetaxel,M-DOC)和普通脂质体(docetaxel liposome,L-DOC)及PEG-2000修饰的长循环脂质体(PEG-2000-modified DOC long circulating liposome,PEG-DOC-LCL)的分布相半衰期分别为(0.17±0.04)、(0.31±0.11)和(0.32±0.06)h,消除相半衰期分别为(8.54±1.05)、(11.18±1.33)和(10.51±1.13)h,表观分布容积分别为(13.66±3.62)、(8.65±1.11)和(6.31±0.55)L,0～24 h曲线下面积分别为(13.45±2.44)、(22.83±3.57)和(29.31±5.96)mg·(h·L)-1,零时间至所有原形药物全部消除时间内的曲线下面积分别为(15.07±2.76)、(28.70±4.95)和(36.95±9.13)mg·(h·L)-1,清除率分别为(1.10±0.18)、(0.54±0.08)和(0.42±0.07)L/h.结论:薄膜分散法制备的DOC脂质体包封率较高,粒径较小;两种DOC脂质体均可不同程度地增加DOC的曲线下面积,降低表观分布容积和清除率,从而延长其在血液循环中的时间,并以用PEG修饰的DOC脂质体效果更好.