Phase I and pharmacokinetic study of two different schedules of oxaliplatin, irinotecan, Fluorouracil, and leucovorin in patients with solid tumors.

PURPOSE: We sought to determine the maximum-tolerated dose (MTD) and evaluate the toxicities and clinical activity of two irinotecan (CPT-11), fluorouracil (FU), leucovorin (LV), and oxaliplatin schedules in patients with advanced solid tumors. Additionally, we investigated the effect of CPT-11 on oxaliplatin pharmacokinetics. PATIENTS AND METHODS: Thirteen patients (cohort 1) received intravenous CPT-11 (infusion) and FU/LV (bolus) on days 1, 8, 15, and 22 and oxaliplatin (infusion) on days 1 and 15 every 6 weeks for a total 37 courses (median, three courses) at three dose levels. Twenty-two cohort 2 patients received intravenous CPT-11/oxaliplatin (infusion, day 1) and FU/LV (90-minute bolus infusion, days 2 to 5) every 3 weeks for a total of 122 courses (median, four courses) at three dose levels. Pharmacokinetic and neurotoxicity assessments were performed at the cohort 2 MTD. RESULTS: Dose-limiting toxicity (DLT) seen in both cohorts at the starting dose required dose de-escalation. Cohort 1 DLT included diarrhea and neutropenia. In cohort 2, diarrhea, vomiting, dehydration, neutropenia, febrile neutropenia, and paresthesias were DLTs. Antitumor activity was seen in both cohorts. In cohort 2, the total platinum area under the curve of patients increased 17% in cycle 2 (P =.048), but objective neurotoxicity was not seen. CONCLUSION: The toxicities resulting from the addition of oxaliplatin to CPT-11/FU/LV are significant but manageable. The MTDs for the weekly schedule are CPT-11 (75 mg/m2), oxaliplatin (50 mg/m2), FU (320 mg/m2), and LV (20 mg/m2); and, for the 3-weekly schedule, the MTDs are CPT-11 (175 mg/m2), oxaliplatin (85 mg/m2), FU (240 mg/m2), and LV (20 mg/m2). Second-cycle platinum accumulation raises the possibility for enhanced cumulative neurotoxicity with CPT-11/oxaliplatin combinations.     

Pharmacokinetics of methotrexate and 7-hydroxy-methotrexate in rabbits

Summary In rabbits the IV kinetics of MTX (1.33, 4 and 12 mg/kg) could be described by a linear three-compartment model with a terminal half-life between 2.4 and 3.6 h. During 8 h 50% of the dose was excreted into urine in unchanged form and 15% as the metabolite 7-OH-MTX. These fractions remained constant with increasing dose. In continuous infusion experiments (9–900 g/kg x min MTX IV) a decrease of the renal MTX clearance with increasing plasma concentration was observed. This effect was nearly compensated by an increase of the extrarenal MTX clearance. After short-term infusion of 7-OH-MTX (4 mg/kg) a biexponential decline of 7-OH-MTX plasma concentrations was observed with a terminal half-life of 0.45 h. About 80% of the dose was regained from urine during 5 h. From the combined pharmacokinetic data a linear model was constructed for the calculation of 7-OH-MTX plasma concentrations after short-term MTX infusion. For the first 4 h after MTX application the predicted values were in good accordance with the 7-OH-MTX concentrations actually measured.     

Clinical pharmacology of deoxyspergualin in patients with advanced cancer

Pharmacokinetic studies were carried out in 25 patients with advanced cancer receiving deoxyspergualin (DSG), a candidate anticancer agent, in a dose-finding Phase I study. The dosage range explored was 80 to 2160 mg/m2/day for 5 days by continuous i.v. infusion. The drug levels in plasma and urine were measured by high-performance liquid chromatography with postcolumn derivatization and fluorescence detection. One drug metabolite was demonstrated in plasma and urine of treated patients. This metabolite was extracted from urine and purified to homogeneity; thereafter, it was examined by high-performance liquid chromatography, nuclear magnetic resonance, and fragmentation mass spectrometry and was demonstrated to be identical to chemically synthesized desaminopropyl-DSG. The mean steady state plasma concentrations of DSG ranged from 0.28 to 11.1 microM at, respectively, the 80- and 2160-mg/m2 dosage levels. The plasma concentration at steady state and the area under the plasma concentration versus time curve of DSG were proportional to dose (r = 0.97). Following discontinuance of the infusion, DSG was cleared from the plasma in a biexponential fashion. The mean total body clearance was 364 +/- 78 ml/min/m2. Desaminopropyl-DSG was formed extensively at all dosage levels; mean steady state plasma levels of this metabolite reached a plateau 2.65 microM at a dose of 720 mg/m2/day and did not rise with further dose increments. The urinary content of DSG was examined in 20 patients over the dosage range from 160 to 960 mg/m2/day; in this group less than 10% of the administered dose was excreted as DSG. In four patients at the 720- and 960-mg/m2/day dosage levels, the total DSG plus metabolite excretion ranged from 7 to 18% of the administered dose, with comparable quantities occurring as the parent drug and desaminopropyl-DSG.     

Prediction of exposure-driven myelotoxicity of continuous infusion 5-fluorouracil by a semi-physiological pharmacokinetic–pharmacodynamic model in gastrointestinal cancer patients

To describe 5-fluorouracil (5FU) pharmacokinetics, myelotoxicity and respective covariates using a simultaneous nonlinear mixed effect modelling approach. Thirty patients with gastrointestinal cancer received 5FU 650 or 1000 mg/m2/day as 5-day continuous venous infusion (14 of whom also received cisplatin 20 mg/m2/day). 5FU and 5-fluoro-5,6-dihydrouracil (5FUH2) plasma concentrations were described by a pharmacokinetic model using NONMEM. Absolute leukocyte counts were described by a semi-mechanistic myelosuppression model. Covariate relationships were evaluated to explain the possible sources of variability in 5FU pharmacokinetics and pharmacodynamics. Total clearance of 5FU correlated with body surface area (BSA). Population estimate for total clearance was 249 L/h. Clearances of 5FU and 5FUH2 fractionally changed by 77%/m2 difference from the median BSA. 5FU central and peripheral volumes of distribution were 5.56 L and 28.5 L, respectively. Estimated 5FUH2 clearance and volume of distribution were 121 L/h and 96.7 L, respectively. Baseline leukocyte count of 6.86 × 109/L, as well as mean leukocyte transit time of 281 h accounting for time delay between proliferating and circulating cells, was estimated. The relationship between 5FU plasma concentrations and absolute leukocyte count was found to be linear. A higher degree of myelosuppression was attributed to combination therapy (slope = 2.82 L/mg) with cisplatin as compared to 5FU monotherapy (slope = 1.17 L/mg). BSA should be taken into account for predicting 5FU exposure. Myelosuppression was influenced by 5FU exposure and concomitant administration of cisplatin.     

Toxicity, pathological effects, and antineoplastic activity of a non-toxic dose of 5-fluorouracil in combination with methotrexate

The survival time of CF-1 mice bearing Ehrlich ascites tumor cells was increased significantly by i.p. administration of a non-toxic dose of 5-fluorouracil (25 mg/kg) followed by methotrexate (40 mg/kg). The effects of 5-fluorouracil (FU) and methotrexate (MTX), singly and in combination, were examined on the hematopoietic system (platelets, erythrocytes, leukocytes, and hematocrit), body weight, and the crypt of Liberkühn to assess toxicity, and on survival of tumor-bearing animals to assess antineoplastic activity. Sequential treatment with a non-toxic dose of FU followed by MTX for 3 consecutive days produced no significant adverse effect. MTX alone and the scheduling of FU after a priming dose of MTX resulted in: (a) a marked decrease in the hematopoietic parameters; (b) significant morphological changes in ileal tissue; and (c) a reduction in body weight. The survival of tumor-bearing animals treated with FU alone and FU 2 hours before MTX was 124% and 139% greater than control, respectively. The survival rate of animals treated with MTX alone was less than that of untreated tumor animals. This study suggests the feasibility of designing FU and MTX regimens that will have little or no systemic toxicity while maintaining antineoplastic activity.     

Methotrexate-vindesine association in the treatment of head and neck cancer Influence of vindesine on methotrexate's pharmacokinetic behavior

Summary Determination of methotrexate (MTX) kinetics after an IV bolus (50 mg/m²) allows prediction of the steady-state plasma level of this drug during a constant infusion. This prediction allows high-dose MTX (HD-MTX) therapy without major toxicity.Patients with head and neck carcinoma received HD-MTX and vindesine (VDS) infusions concomitantly. The therapeutic survey of these patients showed that the predicted plasma level of MTX was not achieved in the presence of VDS. Moreover, the computed dose of MTX had to be increased by a larger amount if the MTX plasma clearance after the identification IV push was low (<9 l/h).In the presence of VDS, the creatinine clearance is lower than when MTX is infused alone, and MTX renal elimination is identical (MTX or MTX+VDS infusions). Thus it seems that the decrease of the MTX plasma level during MTX-VDS infusion could be due to an increase of cellular incorporation.     

Metabolites of 5-fluorouracil in plasma and urine, as monitored by 19F nuclear magnetic resonance spectroscopy, for patients receiving chemotherapy with or without methotrexate pretreatment

19F NMR spectroscopy at 470 MHz (11.7 Tesla) has been used to directly measure the levels of 5-fluorouracil (FU) and its fluorine-containing catabolites in plasma and urine of colon cancer patients after i.v. infusion (10 min) of 60-230 mumol (8-30 mg) FU/kg, either with or without pretreatment with methotrexate (5.1-12.5 mg/kg). With a 1.5-ml sample the minimum metabolite concentration that can be quantified is approximately 15 +/- 5 microM within 30 min and 3 +/- 1 microM within 12 h of data acquisition. The first and second catabolites of FU, dihydrofluorouracil and alpha-fluoro-beta-ureidopropanoic acid, exhibit steady-state behavior with dose-dependent plasma concentrations of 5-40 microM for approximately 10-90 min after infusion (12 patients, 16 treatments). The final catabolite alpha-fluoro-beta-alanine (FBAL) was detected in plasma after 5-15 min, and the rate at which its concentration increased was independent of FU dose, while the maximum concentration reached at about the time FU disappeared (FU less than 5 microM in 1-2 h) was dose-dependent. The area under the time curve for FU in plasma increased more than linearly with dose. Several patients showed elevated levels of free fluoride anion (F-) in plasma (63 samples: median, 5 microM; maximum, 33 microM). In urine all of the above catabolites and F- could be observed. In samples with pH greater than or equal to 7.3 (methotrexate patients, due to bicarbonate infusion) N-carboxy-FBAL was also found in significant amounts. Urinary excretion of FU and catabolites amounted to 2.6-30% of the dose within 2 h (14 patients, 18 treatments) and 60-66% within 24 h (three patients). The ratio FU/creatinine in 2-h urine increased more than linearly with FU dose. Urinary fluoride concentration reached a maximum during the first day after FU infusion and returned to normal background levels after 2-3 days (four patients). The pattern of FU catabolites observed in plasma or urine did not differ significantly between responders and nonresponders to therapy or between patients with FU monotherapy and patients with methotrexate pretreatment. Cytotoxic FU anabolites, i.e., nucleotides, were not detected in plasma or urine (i.e., are less than 3 microM). Their detection in tumor tissue will be required for an assessment of individual responsiveness to FU. Possible toxic metabolic products derivable from FBAL, e.g., 2-fluoroacetate or 2-fluorocitrate, were not detected (i.e., are less than 3 microM) in plasma or urine.(ABSTRACT TRUNCATED AT 400 WORDS)     

Phase I trial of 5-fluorouracil and dipyridamole administered by seventy-two-hour concurrent continuous infusion

Forty-seven patients with advanced malignancies were treated with a concurrent 72-h continuous infusion of 5-fluorouracil (FUra) and dipyridamole. The FUra dose was escalated over the dose range of 185 to 3600 mg/m2/day for 3 days. Dipyridamole was administered in a fixed dose of 7.7 mg/kg/day for 3 days. A total of 155 courses of therapy were completed of which there were 31 paired courses of the combination and FUra alone, at the same dose of FUra and in the same patient. This was for purposes of analysis of pharmacokinetics and modulation of FUra toxicity by dipyridamole. Stomatitis was the dose-limiting toxicity experienced by patients entered into this trial. Myelosuppression was not a serious problem. Increasing FUra plasma concentration was associated with greater leukopenia and stomatitis. Dipyridamole did not appear to modulate the systemic toxicity of FUra. The pharmacokinetics of FUra were altered by the concurrent administration of dipyridamole. Dipyridamole promoted the total body clearance of FUra which resulted in lower mean steady-state FUra plasma concentrations when compared with courses of FUra alone administered at the same dose level. These differences were statistically significant over the course of the trial. For courses of the combination, FUra exhibited linear pharmacokinetics over the dose range studied. Total body clearance of FUra declined slightly at the higher dose levels, but the differences were not significant. For courses of FUra alone, total body clearance was significantly decreased above the dose level of 2300 mg/m2/day. At the maximal tolerated dose of FUra, 2300 mg/m2/day x3, mean steady-state FUra plasma concentration and total body clearance were 6.6 microM and 122 liters/h/m2, respectively, for courses of the combination. The corresponding pharmacokinetic parameters were 7.4 microM and 103 liters/h/m2 for courses when FUra was given alone. Further evaluation of the utility of this regimen and basis of these pharmacokinetic observations appear warranted.     

Second-line chemotherapy with a hybrid-alternating regimen of bolus 5FU modulated by methotrexate and infusional 5FU modulated by folinic acid in patients with metastatic colorectal cancer pretreated with 5FU. A phase 2 study

BACKGROUND AND AIM: In vitro, methotrexate (MTX) is the best modulator for bolus 5-fluorouracil (5FU), whereas folinic acid (FA) is the best for continuous infusion. We evaluated the effect of 5FU modulated by both MTX (bolus administration) and FA (continuous infusion) as second-line treatment of patients with metastatic colorectal cancer. PATIENTS AND METHODS: Entry criteria were: at least one 5FU-based chemotherapy regimen as first-line treatment for metastatic disease, or progression within twelve months after 5FU-containing adjuvant therapy. Treatment schedule: MTX 200 mg/m2 i.v. days 1 and 15; 5FU 600 mg/m2 i.v. bolus, days 2 and 16; 5FU 200 mg/m2 i.v. continuous infusion for 21 days, starting on day 29; FA 20 mg/m2 i.v. bolus weekly during the three weeks of 5FU infusion. Cycles were repeated every 56 days. The primary end-point was tumour control rate, including partial responses and stabilizations. RESULTS: 34/35 patients enrolled were evaluable for response. Five (14.7%) had a partial response, 13 (38.2%) disease stabilization, and 16 (47.1%) progressed; tumour control rate was 52.9%. Median TTP was 5.8 months (95% CI 4.03-7.83); 29 patients had died. Median OAS was 15.9 months (95% CI 8.8-21.9). Toxicity was mild. CONCLUSIONS: The regimen constituted by 5FU modulated by MTX (bolus administration) and FA (continuous infusion) is active as second-line treatment of metastatic colorectal cancer.     

5-fluorouracil modulated by leucovorin, methotrexate and mitomycin: highly effective, low-cost chemotherapy for advanced colorectal cancer

We have reported that an alternating regimen of bolus and continuous infusion 5-fluorouracil (FU) was superior to bolus FU in terms of response rate and progression-free survival in advanced colorectal cancer. Biochemical modulation was an essential part of this regimen and it was selective for the schedule of FU administration: bolus FU was in fact modulated by methotrexate (MTX) while continuous infusion FU was potentiated by 6-s-leucovorin (LV). Considering the low cost and the favourable report on the activity of mitomycin C (mito) added to CI FU, we have incorporated this agent in the infusional part of our treatment programme. 105 patients with untreated, advanced, measurable colorectal cancer were accrued from 13 Italian centres and treated with the following regimen. 2 biweekly cycles of FU bolus (600 mg/m(2)), modulated by MTX (24 h earlier, 200 mg/m(2)) were alternated with a 3-week continuous infusion of FU (200 mg/m(2)daily), modulated by LV (20 mg/m(2)weekly bolus). Mito, 7 mg/m(2), was given on the first day of the infusional period. After a 1 week rest, the whole cycle (8 weeks) was repeated, if indicated. 5 complete and 34 partial responses were obtained (response rate, 37% on the intention to treat basis; 95% confidence limits, 28-46%). After a median follow-up time of 26 months, 37 patients are still alive. The median progression-free survival is 7.7 months with an overall survival of 18.8 months and a 2-year survival rate of 30%. The regimen was very well tolerated with fewer than 13% of patients experiencing WHO grade III-IV toxicity. These results are consistent with those obtained by our group in 3 previous trials of schedule specific biochemical modulation of FU. They also indicate a highly active, little toxic, inexpensive regimen of old drugs to be used (a) as an alternative to the more expensive combinations including CPT-11 or oxaliplatin or (b) as the basis for combination programmes with these agents.     

Influence of piperacillin on the pharmacokinetics of methotrexate and 7-hydroxymethotrexate

The influence of concomitant administration of piperacillin (PIP) on the pharmacokinetic parameters of methotrexate (MTX) and 7-hydroxymethotrexate (7-OH-MTX) was studied in rabbits. Six rabbits received an initial i.v. bolus (0.21 mg kg⁻¹) followed by a constant-rate i.v. infusion of the drug (5 μg min⁻¹ kg⁻¹) for 240 min. The PIP dose (30 mg kg⁻¹) was repeated every 30 min until the end of the infusion period. The control group consisted of four rabbits treated the same way except for the addition of PIP. There were significant increases in the mean residence times found for MTX (MRT_inf) and 7-OH-MTX (MRT_m,inf) following PIP administration. Concomitant administration of PIP with MTX also produced significant 1.5- and 2.8-fold increases in the area under the curve of MTX and 7-OH-MTX, respectively. The total body clearance of MTX and the operative total body clearance of 7-OH-MTX significantly decreased, but in a less than proportional manner. The study demonstrates that the interaction between MTX and PIP is mainly due to the reduced clearance of both MTX and 7-OH-MTX combined with a slight increase in the formation clearance of the metabolite. Received: 9 March 1998 / Accepted: 14 May 1998     

Pharmacokinetics of bolus 5-fluorouracil: relationship between dose, plasma concentrations, area-under-the-curve and toxicity

The pharmacokinetics of 5-fluorouracil (5FU) have been related to toxicity and antitumor activity, in particular for continuous infusion schedules, but to a lesser extent for frequently used bolus injections. The use of intensive sampling schedules limits the application of pharmacokinetics to optimize individual dosing or to define the ideal combination with other drugs. We therefore reanalyzed a pharmacokinetic study in order to develop a limited sampling schedule. Patients received escalating doses of 5FU at 500, 600 and 720 mg/m2 as a bolus until toxicity developed. Blood samples were analyzed until 24 h after administration. The area under the concentration time curve from 0-90 min (AUC(0-90)) was strongly correlated with dose and also with toxicity (p = 0.0009). The 5FU concentrations at 30 and 60 min were correlated to the AUC(30-240) and to that of the AUC(0-90) (r2 = 0.970). The use of limited sampling (30, 60, 90 min) in a patient given 353 mg/m2 5FU with severe toxicity at initial dosing at 500 mg/m2 revealed that the AUC(0-90) at 353 mg/m2 was higher than the normal AUC(0-90) for 500 mg/m2. This patient appeared to have an 8-fold lower activity of the 5FU degradation enzyme dihydropyrimidine dehydrogenase. Limited sampling will allow us to define potential aberrant kinetics of pharmacokinetic interaction of 5FU with other drugs being developed for treatment of colorectal cancer.     

PAC fixed dose: pharmacokinetics of a 1-hour paclitaxel infusion and comparison to BSA-normalized drug dosing

BACKGROUND: The aim of this study was to determine the pharmacokinetics (PKs) of a 175-mg fixed dose of paclitaxel (PAC) after a 1-h infusion in cancer patients and to compare them with the PK parameters from a study with a dose normalized to the body surface area (BSA) (100 mg/m2). PATIENTS AND METHODS: PAC PKs were studied during the first course of therapy in 13 patients. A fixed dose of 175 mg PAC was administered weekly by a 1-h infusion to patients with advanced cancer. Total PAC in serum was quantified by high-performance liquid chromatography (HPLC). PK parameters were calculated by non-compartmental and model-dependent methods. RESULTS: The mean BSA of 12 patients (1 patient excluded from all analyses because of prolonged infusion duration) was 1.79 m2 (coefficient of variation (CV) 7.8%), the mean dose referred to the individual BSAs was 98.3 mg/m2 (CV 8.3%). The mean area under the curve (AUC) was 6,193 ng/ml x h (CV 46%), the mean plasma clearance (Clp) was 19.7 l/h/m2 (CV 45%), and the volume of distribution at steady state (Vss) was 121.6 l/m2 (CV 52%). The mean residence time (MRT) was 7.6 h (CV 46%), the mean distribution half-life (t1/2 alpha) of PAC(tot) was 0.4 h (CV 62%), and the elimination half-life (t1/2 beta) 10.0 h (CV 42%). Maximum plasma concentration Cmax was 3,161 ng/ml (CV 36%). The mean time above 0.05 microM (42.7 ng/ml) was 19.7 h, and the mean time above 0.1 microM (85.4 ng/ml) was 10.6 h. CONCLUSIONS: In this study, a fixed dose of PAC of 175 mg corresponds to a mean BSA-normalized dose of 98.3 mg/m2 (range 88.8-117.4 mg/m2). A higher variability of PK parameters was observed compared to previously published results of a PK study with BSA-normalized dosing of 100 mg/m2. However, the AUC and the time above threshold concentrations did not depend on the dose. Therefore, a fixed dose of 175 mg weekly could be an option for palliative treatment with PAC and may offer a simple but effective schedule for PAC treatment.     

Delayed methotrexate clearance in osteosarcoma patients treated with multiagent regimens of neoadjuvant chemotherapy

We retrospectively studied 790 patients with osteosarcoma treated by neoadjuvant chemotherapy at a single institution between 1983 and 2000 according to different protocols, all including a high dose of methotrexate (HDMTX), to determine the incidence of delayed clearance of HDMTX, and identify patients at high risk for this kind of toxicity. Chemotherapy was administered according to 7 different protocols, successively activated, in which HDMTX was associated with other drugs (cisplatin, adriamycin, ifosfamide) in different combinations. The doses of MTX ranged between 7.5 to 12 g/m(2) and patients received from 1 to 10 cycles with MTX for a total number of 4219 cycles. The incidence of delayed clearance of MTX (plasma values of the drug at 24 h >5 microM/l) was 8.6% per patient and 1.6% per cycle of treatment. In 51 cases the delayed clearance of MTX was "mild" (plasma values of MTX at 24 h between 5 and 19 microM/l) and in 18 cases "severe" (plasma values of MTX at the 24 h >20 microM/l). The delayed clearance of MTX was significantly correlated with the age of patients (16% for patients over 20 vs. 6% for younger patients: p=0.0001) and was significantly more frequent during the first cycles of chemotherapy (7% during the first 3 cycles of treatment vs. 2% during subsequent cycles). There was also a significant correlation (p=0.0001) between the plasma values of MTX at the end of the infusion and at 18 h and the delayed clearance of the drug. In addition to support treatment by increased hydration and sodium bicarbonate, all patients who experienced the delayed clearance of MTX were treated solely with a high dose of leucovorin (HDLV), which was started at the first 18 h. Significant neutropenia and/or thrombocythopenia, increase of serum creatinine, mucositis of varying degrees and vomiting occurred in most cases of severe delayed clearance of MTX, but all patients completely recovered. We conclude that in spite of adequate hydration and urine alkalinization and the use of pharmacokinetically guided leucoverin rescue, delayed clearance of MTX may still occur and that its incidence is higher in older patients and during the first cycles of treatment. However, if "rescue" treatment is started early, the consequent morbility is tolerable and these patients can be rescued using only HDLV, without the need for extracorporeal removal.     

Pharmacokinetics of pyrazoloacridine in the rhesus monkey

Pyrazoloacridine is a rationally synthesized acridine derivative with in vitro activity against solid tumor cell lines, noncycling and hypoxic cells, and tumor cell lines that exhibit the multidrug resistance phenotype. The pharmacokinetic behavior of pyrazoloacridine after a 1- or 24-h i.v. infusion was studied in 5 rhesus monkeys that received a total of 10 courses of pyrazoloacridine at 300 or 600 mg/m2. Pyrazoloacridine levels in plasma and cerebrospinal fluid were measured by high-pressure liquid chromatography. For 1-h infusions, the plasma disappearance was biexponential with a t 1/2 alpha of 31 min and t 1/2 beta of 11 h. The mean volume of distribution at steady state was 1380 liters/m2. The clearance was 1660 ml/min/m2. For the 300 mg/m2 dose, the mean area under the concentration-time curve was 759 microM.min, and the mean peak concentration was 1.3 microM. For the 600 mg/m2 dose, the area under the concentration-time curve was 1330 microM.min, and the peak concentration was 2.5 microM. The steady-state plasma concentrations during the 24-h continuous infusions were 0.27 microM for the 300 mg/m2 dose and 0.45 microM for the 600 mg/m2 dose. The mean clearance calculated from these steady-state concentrations was 2420 ml/min/m2. Cerebrospinal fluid levels were less than 0.1 microM for all doses and schedules. There was no evidence of toxicity at any dose or schedule. These results contrast strikingly with those obtained in mice and dogs in which, despite a more rapid clearance of pyrazoloacridine, significant toxicities were observed at doses that were nontoxic in the monkey. These interspecies differences in the pharmacokinetic and pharmacodynamic behavior of pyrazoloacridine have important implications for the design of Phase I trials in humans.     

Pharmacokinetics of trimetrexate administered by five-day continuous infusion to patients with advanced cancer

The disposition of the methotrexate analogue trimetrexate (TMTX, NSC 352122; 2,4-diammino-5-methyl-6-[(3,4,5-trimethoxyanilino)methyl]qui nazoline) was determined in a Phase I study in 16 patients with refractory or relapsing cancer. The drug was administered by continuous 5-day infusion at doses of 5 to 60 mg/m2/120 h (1-12 mg/m2 daily for 5 days). Plasma and urine collections were made during and after infusion and TMTX levels were quantitated by a specific and sensitive high-performance liquid chromatographic assay. Estimates of pharmacokinetic parameters were similar when determined by either compartmental or noncompartmental methods. There were no significant differences in parameters between the first and second courses of treatment to 10 of the patients. Significant linear relations between TMTX dose and the area under curve of plasma TMTX (r2 = 0.858, P = 0.0001) and the steady-state TMTX plasma level (r2 = 0.764, P = 0.0001) were established. Total TMTX clearance was 30.4 +/- 7.6 (SD) ml/min/m2, renal clearance 7.80 +/- 3.9 ml/min/m2, nonrenal clearance 23.2 +/- 7.1 ml/min/m2, volume of distribution 32.8 +/- 16.6 liters/m2, and terminal half-life 13.4 +/- 7.0 h. The percentage of the trimetrexate dose excreted unchanged in urine ranged from 8.4 to 40.7% (mean, 24.9 +/- 9.2%) and was related to creatinine clearance (r2 = 0.312, P = 0.010). Trimetrexate renal clearance was also related to urine flow (r2 = 0.330, P = 0.008). Trimetrexate pharmacokinetics was linear over the dose range 5 to 60 mg/m2 when given by 5-day continuous infusion to patients but there was evidence of urine flow-dependent renal clearance which requires further examination.     

Renal clearance of methotrexate in man during high-dose oral and intravenous infusion therapy

Summary The renal excretion and clearance of methotrexate (MTX) following high-dose (800 mg) therapy followed by folinic acid rescue was studied in 12 patients (2 female, 10 male): the mean age was 49.3±5.5 (SE), weight 68.6±3.9 (SE) and body surface area 1.8±0.1 m². Plasma and urine were collected over 154 h at intervals of 2–24 h, and the collection times, volume, and pH of urine samples recorded. Total MTX concentrations in urine and plasma were measured by the highly specific competitive protein-binding assay method. Plasma and urinary creatinine levels were measured on an SMA-12 autoanalyser. The renal clearance of MTX was calculated for each urine collection period. Following oral administration, clearance values during the first 6 h were high at 257±8.3 (ml/min), followed by a trough in clearance of 27.9±4.2 (ml/min) in the 20- to 30-h period. This was followed by a secondary rise of MTX renal clearance to 180.4±14.6 ml/min during the 68- to 84-h period and again to 84.9±17.1 ml/min between 84 and 112 h. In the last two periods it rose to 209±57.9 ml/min. Similar fluctuations were seen following IV administration. The changes in clearance were statistically significant at the P<0.005 level. It is suggested that high concentrations of MTX in the renal tubules result in inhibition of carrier protein synthesis, leading to a fall in active tubular secretion. When MTX concentrations fall the tubular cell recovers and a secondary rise in renal clearance occurs, leading to cyclical changes in MTX elimination.     

Phase I clinical and pharmacological study of 72-hour continuous infusion of etoposide in patients with advanced cancer

Etoposide (VP-16) is a semisynthetic epipodophyllotoxin that exhibits cell cycle phase specific cytotoxicity and enhanced effectiveness with increasing duration of drug exposure. We have therefore conducted a Phase I trial to determine the side effects, tolerable doses, and pharmacokinetic parameters of VP-16 given by continuous i.v. infusion to patients with advanced cancer. Eighteen patients were treated with varying dosages of VP-16 infused continuously for 72 consecutive hours every 28 days. Using this schedule, the maximally tolerated dosage of VP-16 was 150 mg/m2/day for patients with good performance status and 125 mg/m2/day for more debilitated cancer patients. Hematological toxicity was dose limiting with median granulocyte and platelet nadirs of 700/mm3 and 116,000/mm3, respectively, at a dose of 150 mg/m2/day. Other toxicities included only mild nausea, vomiting, and alopecia. Plasma and urine VP-16 concentrations were determined using a high-performance liquid chromatography assay. At a VP-16 dosage of 150 mg/m2/day, steady-state VP-16 concentrations were in the range of 2.1 to 7.0 micrograms/ml in all patients. Further pharmacokinetic analysis revealed that the plasma clearance of VP-16 was consistently near 25 ml/min/m2 (independent of dosage) and that renal clearance accounted for only 15% of VP-16 total plasma clearance. Patient age was found to be the most important factor correlating with plasma clearance of VP-16. Linear regression analysis also revealed that both the plasma VP-16 concentration at steady state and the concentration of VP-16 in plasma at 24 h from the start of the infusion correlated with hematological toxicity; no other patient characteristics correlated with hematological toxicity. The recommended VP-16 dose for Phase II trials of 72-h continuous infusion VP-16 is 150 mg/m2/day in patients with good performance status.     

Pharmacokinetic study of etoposide in aged patient with non Hodgkin lymphoma receiving hemodialysis

A 78 year old patient with non Hodgkin Lymphoma receiving hemodialysis was treated with etoposide at a dose of 50 mg per body and its plasma pharmacokinetics were studied. The patient was dialyzed for 4 hours three times weekly. Etoposide was given by 60 minutes infusion on day 1 and 3, and hemodialysis was performed on day 2. The pharmacokinetic curve was found to fit to two compartment model. T 1/2 beta was 11.29 hours. Total body clearance was 13.65 mg/min/m2 on day 1 and 12.83 mg/min/m2 on day 3 respectively. AUC was 41.53 micrograms.h/ml on day 1 and 44.18 micrograms.h/ml on day 3 respectively. When these results were compared to those reported in patients with normal renal function, half life were longer while total body clearance was lower. In addition, AUC was higher. Hematologic toxicities were severe at this low dose. Hemodialysis did not influence on the decay of concentration during the elimination phase. These results suggest that it is necessary to reduce the dose of etoposide in hemodialysis patients.