Multifunctional nanoparticles encapsulating methotrexate and curcumin for holistic management of rheumatoid arthritis: in-vitro and pre-clinical assessment.

PURPOSE: Bovine serum albumin (BSA) nanoparticles (BSA-MTX-CUR-NPs) encapsulating methotrexate (MTX) and curcumin (CUR) was developed with an aim to co-deliver the drugs at the inflamed joint so as to maximize the therapeutic efficacy and alleviate toxic side effects associated with MTX. METHODS: Nanoparticle albumin-bound technology was used to formulate nanoparticles, followed by characterization for its particle size, polydispersity index, encapsulation efficiency, zeta potential, surface morphology, in-vitro drug release and drug release kinetics. Further, we investigated the pharmacokinetics and pharmacodynamics of the developed nanoparticles in the adjuvant-induced arthritis model. RESULTS: BSA-MTX-CUR-NPs exhibited particle size of 163.05 ± 1.708 nm, polydispersity index of 0.195 ± 0.0024 and % encapsulation efficiency of 68.23 ± 0.640% for MTX and 75.71 ± 0.216% for CUR with controlled release pattern for both the drugs. The scanning electron microscopy revealed nanoparticles exhibited a spherical shape. DSC study confirmed the absence of incompatibility between the drugs and the excipients. Half-life and area under the curve were significantly higher for MTX in the nanoparticulate form in comparison to free MTX. Pharmacodynamic studies revealed that BSA-MTX-CUR-NPs possessed better disease-modifying effects in comparison to free MTX. CONCLUSION: Hence, it can be concluded that albumin nanoparticles constitute a viable method for delivering MTX and CUR to inflamed joints simultaneously, because of the strong affinity of albumin and enhanced permeability and retention effect at the inflamed joint. This combinational therapy of MTX & CUR in nanoparticulate form has the potential for the holistic management of rheumatoid arthritis.

Urine volume to hydration volume ratio is associated with pharmacokinetics of high-dose methotrexate in patients with primary central nervous system lymphoma.

High-dose methotrexate (HD-MTX)-based chemotherapy is the first-line treatment for primary central nervous system lymphoma (PCNSL), but is associated with severe adverse effects, including myelosuppression and renal impairment. MTX is primarily excreted by the kidneys. Renal function calculated using serum creatinine (Scr) derived from muscle may be overestimated in elderly PCNSL patients. Therefore, we aimed to construct a population pharmacokinetic model in PCNSL patients and explore the factors associated with MTX clearance. Sixteen PCNSL patients (median age, 66 years) treated with HD-MTX were included, and serum MTX concentrations were measured at 193 points in 49 courses. A population pharmacokinetic analysis was performed using NONMEM. A Monte Carlo simulation was conducted, in which serum MTX concentrations were stratified into three groups of creatine clearance (Ccr) (50, 75, and 100 ml/min) with three groups of the urine volume to hydration volume (UV/HV) ratio (<1, 1-2, and >2). The final model was constructed as follows: MTX clearance = 4.90·(Ccr/94.5)0.456 ·(UV/HV)0.458 . In the Monte Carlo simulation, serum MTX concentrations were below the standard values (10, 1, and 0.1 µM at 24, 48, and 72 h, respectively, after the start of the MTX administration) in most patients with UV/HV >2, even with Ccr of 50 ml/min. Conversely, half of the patients with UV/HV <1 and Ccr of 50 ml/min failed to achieve the standard values. The present results demonstrated that the UV/HV ratio was useful for describing the pharmacokinetics of MTX in PCNSL patients.

Exploratory Assessment of Oxygen Flow-Assisted Cutaneous Administration of Methotrexate for Superficial Basal Cell Carcinoma, Mycosis Fungoides, and Extramammary Paget Disease.

The molecular weight of methotrexate (MTX) makes cutaneous penetration difficult. Oxygen flow could enhance the skin permeation of MTX diluted in the proprietary LP3 carrier system. This pilot study aims to assess the efficacy, safety, and tolerance of oxygen flow-assisted LP3-MTX3% for treating superficial skin cancers. Patients with superficial basal cell carcinoma (n = 12), extramammary Paget disease (n = 5), classic mycosis fungoides (MF; n = 10), and folliculotropic MF (n = 6) were included in the study and were treated with four weekly applications of oxygen flow-assisted LP3-MTX3%. Photographs and biopsies were performed before and one month after treatment. At one month after treatment, the mean superficial basal cell carcinoma erythema-crusting-thickness clinical score, the extramammary Paget disease erythema-oozing-scaling/hyperkeratosis-pain/pruritus clinical score, and the modified composite assessment of index lesion severity classic MF and folliculotropic MF scores were improved by 77.5% ± 17.1% (P < 0.0001), 66.7% ± 22.9% (P = 0.011), 51.3% ± 32.2% (P = 0.0007), and 27.8% ± 32.0% (P = 0.086), respectively. At one month after treatment, histology revealed partial and total clearances for superficial basal cell carcinoma (1/12, 11/12), extramammary Paget disease (4/5, 1/5), classic MF (8/10, 2/10), and folliculotropic MF (6/6, 0/6). Tolerance was excellent and no pain was observed. MTX was never detectable in serum at baseline and 1, 2, 3, 8, 24, 48, and 72 hours post-treatment. In conclusion, the interesting therapeutic efficacy of oxygen flow-assisted LP3-MTX3% for treating superficial basal cell carcinoma, extramammary Paget disease, and MF lesions prompts further studies on a larger scale.

Exposure-Response Modeling and Power Analysis of Components of ACR Response Criteria in Rheumatoid Arthritis (Part 2: Continuous Model).

Population pharmacokinetic/pharmacodynamic (PK/PD) models were developed to quantitate the exposure-response relationships using continuous longitudinal data on American College of Rheumatology (ACR) subcomponents, that is, tender-joint count (TJC), swollen-joint count (SJC), C-reactive protein, patient's assessment of pain, patient's global assessment of disease activity, physician's global assessment of disease activity, and patient's assessment of physical function for 5 biologics approved for use in rheumatoid arthritis. The models were then used to simulate the time courses of clinical outcomes following different treatment regimens. The relative sensitivity of the 7 subcomponents was assessed using Monte Carlo simulation-based power analysis. The developed population PK/PD models adequately described the relationship between serum concentrations and changes in ACR subcomponents. The trial simulation and subsequent power analysis showed that SJC and TJC appeared to be more sensitive than the other 5 ACR subcomponents to detect treatment effect over placebo/methotrexate. These 7 ACR subcomponents had similar power in detecting the treatment difference between different doses. In addition, the continuous measures of ACR subcomponents did not appear to be more sensitive than binary measures.

Exposure-Response Modeling and Power Analysis of Components of ACR Response Criteria in Rheumatoid Arthritis (Part 1: Binary Model).

American College of Rheumatology (ACR) response criteria is used to assess improvement in tender and swollen joint counts and in 3 of the 5 core measures (acute-phase reactant, physician global assessment, patient global assessment, pain, and physical function). From the clinical trial data on 5 approved biological products for the treatment of rheumatoid arthritis, population pharmacokinetic/pharmacodynamic models were developed to quantitatively describe the relationship between exposure and response rates of 3 individual components of ACR response criteria. The models were then used to simulate the clinical outcomes at various time points following different treatment regimens. The relative sensitivity of these criteria components was assessed using power analysis. As compared to the composite endpoints (ACR20/ACR50/ACR70), the individual ACR criteria components had adequate power and higher sensitivity in distinguishing treatment effects over placebo/methotrexate control. The 3 individual ACR criteria components appeared to have similar powers at different dose levels after long-term treatment. This research provides a unique approach to assess the relative sensitivity of the 3 binary components of ACR response criteria which would be useful to support future dose selection and trial design in the treatment of rheumatoid arthritis.

Comparable efficacy with varying dosages of glucarpidase in pediatric oncology patients.

BACKGROUND: Glucarpidase rapidly reduces methotrexate plasma concentrations in patients experiencing methotrexate-induced renal dysfunction. Debate exists regarding the role of glucarpidase in therapy given its high cost. The use of reduced-dose glucarpidase has been reported, and may allow more institutions to supply this drug to their patients. This report explores the relationship between glucarpidase dosage and patient outcomes in pediatric oncology patients. METHODS: The authors evaluated data from 26 patients who received glucarpidase after high-dose methotrexate. Decrease in plasma methotrexate concentrations and time to renal recovery were evaluated for an association with glucarpidase dosage, which ranged from 13 to 90 units/kg. RESULTS: No significant relationship was found between glucarpidase dosage (units/kg) and percent decrease in methotrexate plasma concentrations measured by TDx (P > 0.1) or HPLC (P > 0.5). Patients who received glucarpidase dosages <50 units/kg had a median percent reduction in methotrexate plasma concentration of 99.4% (range, 98-100) measured by HPLC compared to a median percent reduction of 99.4% (range, 77.2-100) in patients who received ≥50 units/kg. Time to SCr recovery was not related to glucarpidase dosage (P > 0.8). CONCLUSIONS: The efficacy of glucarpidase in the treatment of HDMTX-induced kidney injury was not dosage-dependent in this retrospective analysis of pediatric oncology patients.

Assessment of the relationship between methotrexate polyglutamates in red blood cells and clinical response in patients commencing methotrexate for rheumatoid arthritis.

BACKGROUND AND OBJECTIVES: Therapeutic drug monitoring in patients with rheumatoid arthritis (RA) receiving methotrexate (MTX, MTXGlu1) has not been established. In this study, we aim to explore the relationship between red blood cell (RBC) concentrations of MTX and its polyglutamate metabolites (MTXGlu(n); n = 2, 3, 4, 5) and clinical response in RA patients commencing MTX. METHODS: The binding activity of MTXGlu(n) to three putative enzymes involved in the MTX mechanism of action­dihydrofolate reductase, thymidylate synthase, and 5-aminoimidazole-4-carboxamide ribonucleotide transformylase­was simulated. RBC MTXGlu(n) concentrations that gave the highest inhibition activity across all three enzymes were linked with the disease activity score DAS28-3v (C-reactive protein [CRP]). A population pharmacokinetic-pharmacodynamic model was developed to describe the relationship between RBC MTX polyglutamate concentrations and clinical response in 12 RA patients commencing MTX. RESULTS: The highest inhibition activity was with RBC MTXGlu(3-5). These polyglutamates were further evaluated for their relationship with DAS28-3v (CRP). Three of the 12 patients had a high DAS28-3v (CRP) at baseline (mean = 6.1) and showed a delayed response to MTX treatment. The remaining nine patients with a lower DAS28-3v (CRP) baseline (mean = 3.6) showed an immediate response. The developed MTX pharmacokinetic-pharmacodynamic model provided an acceptable description of the observed DAS28-3v (CRP) across all patients. CONCLUSIONS: The developed model describes a longitudinal relationship between RBC MTXGlu(3-5) concentrations and DAS28-3v (CRP) in patients with RA commencing MTX. Further work is required to determine whether measurement of RBC MTX polyglutamates might be useful for dose individualisation in patients with RA.

A validated LC-MS/MS method for rapid determination of methotrexate in human saliva and its application to an excretion evaluation study.

A sensitive and simple method for the methotrexate quantification was developed using aminopterin as internal standard. Methotrexate is an anticancer agent that is widely used in a variety of human cancers including primary central nervous system lymphoma. The compound was quantified by liquid-chromatography coupled to electrospray ionization (positive ion-mode) low-energy collision dissociation-tandem mass spectrometry. Quantitative detection was by multiple reaction monitoring of the transitions of the [M+H]+ ion of MTX to its common product ion at m/z 308.4 and of aminopterin at m/z 441.2→m/z 294.0. The method demonstrated linearity over at least three orders of magnitude and had a detection limit of 1ng/ml for methotrexate. A run time of less than 8.0min for each sample made it possible to analyze a large number of human saliva samples per day. Application of this procedure was demonstrated to a saliva excretion study of methotrexate on the samples obtained after an intravenously administration of 1mg/kg/dose of methotrexate to six patients with acute lymphoblastic leukemia.

Biological monitoring of occupational exposure to antineoplastic drugs in hospital settings.

BACKGROUND: In view of the evidence of cytotoxicity of chemotherapic antineoplastic drugs (AD), current guidelines recommend the evaluation of the health risks of hospital personnel exposed to these compounds. Biological monitoring is the main tool to evaluate all possible drug intake and measure workers' real risk. OBJECTIVES: The aim of this study was to assess occupational exposure toAD in a large hospital in Northern Italy in order to verify the effectiveness of the structural and procedural improvements carried out over the last decade. METHODS: Three biological monitoring campaigns were performed using LC-MS/MS analysis of cyclophosphamide (CP) and metotrexate (MTX) as biomarkers of internal dose in the urine of hospital workers. In the first two campaigns, 50 and 81 workers respectively were monitored during AD preparation operations. The last campaign, concerning AD administration activity, was performed after a centralized preparation unit had been set up. Two environmental monitoring campaigns were carried out as well, to complete AD exposure assessment. RESULTS: During the first monitoring campaign we found positive urinary samples in all the wards studied (total positivity 36%), whereas in the second campaign 11% of the samples were positive and four departments showed negative results in all urine samples. The last campaign showed all urinary CP and MTX levels below the detection limit of the analytical method CONCLUSION: Exposure of oncology ward nurses considerably decreased due to the centralization of AD preparation operations together with training and education of workers. The last biological monitoring results were reassuring; nevertheless, surface contamination still occurred and safety measures should be further improved in order to achieve the lowest reasonably possible contamination levels.

In vitro risk assessment of AZD9056 perpetrating a transporter-mediated drug-drug interaction with methotrexate.

Methotrexate is the most commonly used drug to treat rheumatoid arthritis. Since clinical efficacy studies in rheumatoid arthritis are conducted on a background of methotrexate therapy, it is necessary to assess the potential of rheumatoid arthritis candidate drugs to perpetrate a drug-drug interaction (DDI) with methotrexate during development. Consequently, we need to identify the regulatory in vitro studies required to facilitate this assessment. We therefore reviewed the literature to ascertain the methotrexate disposition pathways implicated with known DDIs. Experiments were conducted to confirm that methotrexate was identified as a substrate for these pathways in our laboratory. The literature indicated active renal elimination (mediated by the human transporters OAT1, OAT3, MRP2 and BCRP) to be the principal pathway for methotrexate DDI risk. With the exception of MRP2, methotrexate was confirmed as a substrate of these transporters using oocyte and membrane vesicle test systems. A rheumatoid arthritis candidate drug (AZD9056) and sulfasalazine were subsequently assessed as inhibitors of OAT1, OAT3 and BCRP to determine their DDI potential towards methotrexate. AZD9056 was neither an inhibitor of OAT1 nor OAT3 and did not inhibit their transport of methotrexate. AZD9056 was an inhibitor of BCRP and weakly inhibited BCRP-mediated transport of methotrexate (IC(50)=92µM). Sulfasalazine inhibited methotrexate transport mediated by all transporters studied (IC(50)<5µM). Subsequent assessment of the in vitro data using [I]/IC(50) ratios indicated that both AZD9056 and sulfasalazine were unlikely to cause a DDI with methotrexate in vivo. In conclusion, to support rheumatoid arthritis drug development it is proposed that regulatory in vitro studies for OAT1, OAT3 and BCRP inhibition be routinely conducted to assess the potential for a transporter-mediated DDI with methotrexate in vivo.

Assessment and management of methotrexate hepatotoxicity in psoriasis patients: report from a consensus conference to evaluate current practice and identify key questions toward optimizing methotrexate use in the clinic.

Experts in psoriasis, hepatology, pharmacokinetics and pharmacogenetics convened to discuss the safety and monitoring of methotrexate with respect to hepatotoxicity when used in the treatment of psoriasis. Methotrexate is an efficacious and cost-effective treatment for psoriasis, but is associated with significant safety issues, particularly relating to hepatotoxicity. Current British, Dutch, German, EU and US guidelines for baseline evaluations, monitoring and prevention of hepatotoxicity in patients with psoriasis receiving methotrexate were evaluated. Liver safety monitoring is currently reliant upon multiple methods, including biopsy, serological tests for biomarkers such as type III procollagen amino terminal propeptide (PIIINP), and liver function tests based on liver enzymes. Monitoring of patients receiving long-term therapy is expected to be improved by the utilization of serum biomarkers currently in development such as the Enhanced Liver Fibrosis (ELF) panel and other non-invasive tests of hepatic architecture, such as fibroelastography, microbubbles and magnetic resonance imaging. Appropriate studies to determine optimal dosing to maximize efficacy and minimize toxicity, potentially utilizing pharmacogenetic principles, are clearly needed. Key questions for future research are identified including needs for optimal screening and monitoring, identification of appropriate biomarkers, assessment of relationships between dosing and safety, utility of liver biopsy, optimal dosing regimens (including route of administration), methods to measure methotrexate levels in blood, and use of methotrexate as a standardized active comparator in trials of experimental drugs used to treat psoriasis.

Power estimation using a population pharmacokinetics model with optimal design by clinical trial simulations: application in pharmacokinetic drug-drug interaction studies.

OBJECTIVES: The aim of this article was to determine the power for pharmacokinetic interaction investigations using population a pharmacokinetic modelling approach with optimal sampling designs and clinical trial simulations. METHODS: A clinical trial simulation approach was proposed to estimate the power for pharmacokinetic effects in drug-drug interaction (DDI) studies. This approach consisted of: (1) population pharmacokinetic (PK) model(s) was characterised for the drug(s) studied; (2) D-optimal design strategy was applied based on these model(s) to determine optimal sampling times for DDI investigation; (3) clinical trial simulations under particular study designs, for example a randomised parallel design, were used to evaluate the sample size needed for studying PK interaction. The approach was described using an example investigating the impact of a new anti-inflammatory drug on methotrexate (MTX) exposure in rheumatoid arthritis (RA) patients. RESULTS: The power for evaluating PK interaction largely depended on the interindividual variability (IIV) in PK parameters. Residual variability was also influential to a lesser degree in the sample size determination using the proposed approach. It required 40-60 participants for scenarios where IIV was relatively low in order to achieve 90% power. However, a sample size of 80 individuals was required to reach 90% power where both IIV and residual variances were high. Under the same IIV assumptions, the proposed approach in general required a smaller sample size compared with the standard noncompartmental analysis method with intensive blood samples to attain the target power. When IIV was low, the difference in the power between the two approaches was relatively small. CONCLUSIONS: Population PK modelling with optimal design and clinical trial simulation to determine sample size when designing drug-drug interaction studies was efficient and cost effective.

High dose methotrexate population pharmacokinetics and Bayesian estimation in patients with lymphoid malignancy.

The purpose of present study was to develop a population pharmacokinetic model of high dose methotrexate (HD-MTX) infusion in patients with lymphoid malignancy, to investigate the biological and clinical covariates related to the drug distribution and elimination. It is also the purpose to propose a limited sampling strategy (LSS) for the estimation of the time above the threshold (0.2 micromol.L(-1)). A total 82 patients with lymphoid malignancy were involved in the study. A pharmacokinetic model was developed using nonlinear mixed-effect model. The influence of demographic characteristics, biological factors, and concurrent administration were investigated. The final predictive performance was validated by bootstrap and cross-validation. Bayesian estimation was evaluated. The pharmacokinetics of HD-MTX was described by a two-compartment model. The pharmacokinetic parameters and the inter-individual variability were as follows: the clearance CL, 7.45 L.h(-1) (inter-individual variability 50.6%), the volume of the central and peripheral compartment V(1), 25.9 L (22.5%), V(2), 9.23 L (97.8%), respectively, and the intercompartmental clearance Q, 0.333 L.h(-1) (70.4%). The influence of serum creatinine on CL and weight on V(1) was retained in the final model. The protocol involved one sampling time at 44 h after the start of the infusion, allowing one to predict the time at which the MTX concentration reached the expected threshold (0.2 micromol.L(-1)). Serum creatinine and weight showed significant influence on methotrexate CL and V(1), respectively. Furthermore, a Bayesian estimation based on the covariates and 44 h sample was developed, allowing prediction of the individual methotrexate pharmacokinetic parameters and the time to 0.2 micromol.L(-1).

A mass spectrometry based functional assay for the quantitative assessment of ABC transporter activity.

ATP-Binding Cassette (ABC) transporters are highly expressed in pharmacological barriers limiting the access of drugs to their targets. Since characterization of a compound as a transporter substrate or inhibitor bears significant consequences in drug development, there is a great need for reliable tools that enable the rapid analysis of the transport susceptibility of drugs. Here we describe a simple but very efficient high-performance liquid chromatography/mass spectrometry (HPLC/MS) assay for measuring the ABC transporter-dependent vesicular transport of compounds. In addition, we provide evidence that the requirement for sample preparation can be minimized using desorption electrospray ionization (DESI)-MS, paving the way for a direct, high-throughput investigation of drug-transporter interactions.

[Fish oil supplementation in rheumatoid arthritis]. / La supplementazione dietetica con olio di pesce nell'artrite reumatoide.

The beneficial properties of fish oil are well known and are related to its fatty acid composition rich in omega-3 polyunsaturated fatty acids. In the last years a variety of epidemiological and clinical studies have demonstrated the efficacy of fish oil supplementation in the rheumatic diseases, in particular in rheumatoid arthritis. The anti-inflammatory effects of fish oil are linked to the production of alternative eicosanoids, to the reduction of proinflammatory cytokines, to the inhibition of the activation of T lymphocytes and of catabolic enzymes. Fish oil supplementation could represent a valuable support to the traditional pharmacological treatment of rheumatoid arthritis.

High-dose methotrexate in adults with osteosarcoma: a population pharmacokinetics study and validation of a new limited sampling strategy.

Preoperative high-dose methotrexate (HD-MTX) with folinic acid (leucovorin) rescue is still a mainstay in the treatment of osteosarcoma. This anticancer agent is characterized by a narrow therapeutic index and wide interpatients variability. To ensure effective and safe administration of HD-MTX, we had earlier developed an adaptive-dosing schedule with a feedback strategy. In our institute, the MTX dosage was tailored according to individual pharmacokinetics parameters, determined in real time both from two blood samples (3.5 and 4.5 h) and from Bayesian population parameters. Up to 20 g of MTX was safely administered as 8-h infusions. Low MTX elimination rate has, however, been reported in 15-20% of the patients, and forecasting the MTX elimination phase and the management of leucovorin rescue is still a challenging issue in clinical oncology. This study aims at identifying the clinical or biological covariates related to impaired MTX clearance, and at validating a new limited sampling strategy (LSS), allowing for the accurate prediction of the MTX terminal elimination phase. This retrospective study was carried out on 49 patients (30 men, 19 women; mean age, 26.7 years) treated for osteosarcoma with HD-MTX. The population and individual pharmacokinetics parameters were computed, before the identification of the relevant covariates. Different LSSs were then tested, to predict accurately when the MTX plasma concentrations would drop below 0.2 micromol/l, the threshold associated with the end of the rescue of leucovorin with alkaline hydration. Two main covariates (creatinemia clearance and alanine aminotransferase) were correlated with MTX clearance. Conversely, the impact of body surface area on MTX pharmacokinetics was weak, suggesting that dosing schedules based on body surface area were inadequate and potentially hazardous. A new LSS predicting accurately when the MTX concentration would reach 0.2 micromol/l has been validated; blood samples are stopped as soon as the MTX concentration drops to 1 micromol/l. With this LSS, our retrospective study suggests that 60% of the patients would have left the hospital earlier than they actually did owing to a better forecasting of the MTX decrease, thus improving their quality of life while improving the cost-effectiveness for the institute. HD-MTX can be administered safely using an adaptive-dosing strategy with drug monitoring. Moreover, pharmacokinetic modeling permits the accurate forecasting of the MTX elimination profile, thus allowing for a better management of the postinfusion care of cancer patients treated with particularly high doses of this drug.

Population pharmacokinetics of high-dose methotrexate in children with acute lymphoblastic leukaemia.

OBJECTIVE: To develop and a priori validate a methotrexate population pharmacokinetic model in children with acute lymphoblastic leukaemia (ALL), receiving high-dose methotrexate followed by folinic acid rescue, identifying the covariates that could explain part of the pharmacokinetic variability of methotrexate. METHODS: The study was carried out in 49 children (aged 6 months to 17 years) who received high-dose methotrexate (3 g/m(2) per course) in long-term treatment. In an index group (37 individuals; 1236 methotrexate plasma concentrations), a population pharmacokinetic model was developed using a nonlinear mixed-effects model. The remaining patients' data (12 individuals; 278 methotrexate plasma concentrations) were used for model validation. Age, sex, total bodyweight (TBW), height, body surface area, lowest urine pH during infusion, serum creatinine, ALT, AST, folinic acid dose and length of rescue were analysed as possible covariates. The final predictive performance of the pharmacokinetic model was tested using standardised mean prediction errors. RESULTS: The final population pharmacokinetic model (two-compartmental) included only age and total bodyweight as influencing clearance (CL) and volume of distribution of central compartment (V(1)). For children aged < or =10 years: CL (L/h) = 0.287 . TBW(0.876); V(1) (L) = 0.465 . TBW, and for children aged >10 years: CL (L/h) = 0.149 . TBW; V(1) (L) = 0.437 . TBW. From the base to the final model, the inter-individual variabilities for CL and V(1) were significantly reduced in both age groups (30-50%). The coefficients of variation of the pharmacokinetic parameters were <30%, while residual and inter-occasional coefficients maintained values close to 40%. Validation of the proposed model revealed the suitability of the model. CONCLUSION: A methotrexate population pharmacokinetic model has been developed for ALL children. The proposed model could be used in Bayesian algorithms with a limited sampling strategy to estimate the systemic exposure of individual patients to methotrexate and adapt both folinic acid rescue and methotrexate dosing accordingly.

[Assessment of elimination and tolerance of high dose of methotrexate (3 g/m2) in children with standard-risk acute lymphoblastic leukemia]. / Ocena eliminacji i tolerancji wysokiej dawki metotreksatu (3 g/m2) u dzieci z ostra bialaczka limfoblastyczna standardowego ryzyka.

We assessed correlation between the elimination of methotrexate administered in dose 3 g/m2 during consolidation phase and the early complications in 129 children treated for acute lymphoblastic leukemia. Among 500 chemotherapy cycles included in the analysis the elimination of methotrexate was delayed in 66 (13.2%) cycles in 43 (33.3%) of patients. Influence of methotrexate on selected liver and renal function tests was analyzed. We made an attempt of early identification of patients with high risk for delayed methotrexate elimination and subsequent toxicities.