Plasma Methotrexate Concentrations Research Articles

Adherence to low-dose methotrexate in children with juvenile idiopathic arthritis using a sensitive methotrexate assay

BackgroundLow-dose weekly methotrexate (MTX) is the mainstay of treatment in juvenile idiopathic arthritis. Unfortunately, a substantial part of patients has insufficient efficacy of MTX. A potential cause of this inadequate response is suboptimal drug adherence. The aim of this study was to assess MTX adherence in juvenile idiopathic arthritis patients by quantification of MTX concentrations in plasma. Secondly, the association between MTX concentrations and either self-reported adherence issues, or concomitant use of biologics was examined.MethodsThis was a retrospective, observational study using plasma samples from juvenile idiopathic arthritis patients. An ultrasensitive liquid chromatography-tandem mass spectrometry method was developed for quantification of MTX and its metabolite 7-hydroxy-MTX in plasma. The determined MTX plasma concentrations in juvenile idiopathic arthritis patients were compared with corresponding adherence limits, categorising them as either adherent or possibly non-adherent to MTX therapy.ResultsPlasma samples of 43 patients with juvenile idiopathic arthritis were analysed. Adherence to MTX in this population was 88% shortly after initiation of MTX therapy and decreased to 77% after one year of treatment. Teenagers were more at risk for non-adherence (p = 0.002). We could not find an association between MTX adherence with either self-reported adherence issues, nor with the use of concomitant biological treatment (p = 1.00 and p = 0.27, respectively; Fisher’s Exact).ConclusionsQuantification of MTX in plasma is a feasible and objective method to assess adherence in patients using low-dose weekly MTX. In clinical practice, the use of this method could be a helpful tool for physicians to refute or support suspicion of non-adherence to MTX therapy.

Pharmacokinetics of Anti-Rheumatic drugs Methotrexate and Tofacitinib with its metabolite M9 in Rats by UPLC-MS/MS.

Tofacitinib is an oral JAK inhibitor for the treatment of rheumatoid arthritis (RA). The clinical efficacy and safety of an administered tofacitinib, either monotherapy or in combination with conventional synthetic disease-modifying anti-rheumatic drugs, mainly methotrexate (MTX), have been evaluated. The high plasma concentration with delayed medicine clearance may affect the liver and/or kidney functions. In this study, an ultra-performance liquid chromatography-tandem mass spectrometry (UPLC- MS/MS) method for the quantitative analysis of methotrexate, tofacitinib, and metabolite M9 in plasma of Sprague Dawley (SD) rats was developed, and its effectiveness was validated as well. Methotrexate, tofacitinib, M9 and fedratinib (internal standard, IS) were separated by gradient elution. The chromatography was performed on an Acquity BEH C18 (2.1 mm × 50 mm, 1.7 μm) column with the mobile phases of acetonitrile and 0.1% formic acid aqueous solution with different proportions at the flow rate of 0.30 mL/min. In the positive ionization mode, the analyzes were detected using a Xevo TQ-S triple quadrupole tandem mass spectrometer, with the following mass transition pairs: m/z 313.12 → 148.97 for tofacitinib, m/z 329.10 → 165.00 for M9 and m/z 455.12 → 308.05 for methotrexate. The obtained results manifested good calibration linearity over the ranges of tofacitinib at 0.1-100 ng/mL, M9 at 0.05-100 ng/mL, and methotrexate at 0.05-100 ng/mL. The lower limit of quantifications (LLOQs) of methotrexate, tofacitinib and M9 were 0.05 ng/mL, 0.1 ng/mL and 0.05 ng/mL, respectively. Intra-day and inter-day accuracy values were confirmed with a range of -6.3% to 12.7%, while intra-day and inter-- day precision values were ≤14.4%. Additionally, recoveries were greater than 86.5% for each compound without significant matrix effects. The currently established analytical method exhibited great potential for the evaluation of plasma concentrations of methotrexate, tofacitinib and M9 simultaneously, greatly reducing the detection time, which would serve as a supplementary role in formulating dose decisions to achieve personalized treatment, identify drugs that cause adverse reactions and finally, to assess drug-drug interactions on clinical studies.

The effect of the plasma methotrexate concentration during high-dose methotrexate therapy in childhood acute lymphoblastic leukemia

Two hundred and thirty-one acute lymphoblastic leukemia (ALL) children with 1376 high-dose methotrexate (HD-MTX) courses (3–5 g/m2) were enrolled to analyze the influence of the plasma MTX concentration (C MTX) in ALL. The 24-h target peak C MTX (C 24h) was set at 33 μmol/l for low-risk (LR) and 65 μmol/l for intermediate/high-risk (IR/HR) groups. The median C 24h was 42.0 μmol/l and 69.7 μmol/l for LR and IR/HR groups, respectively. MTX excretion delay was observed in 14.6% of courses, which was more frequent in IR/HR groups (56.9% vs. LR group 40.2%, p = .014) and T-ALL patients (82.6% vs. B-ALL 47.1%, p = .001). MTX-related toxicities were more common in courses with MTX excretion delay. However, survival between the patients who failed to reach the target C 24h or not, with or without MTX excretion delay, was comparable. These findings suggest that, owing to the effectiveness of risk stratification chemotherapy, C MTX does not exert an independent influence on the prognosis of childhood ALL.

Correlation between methylation level of the SLC19A1 promoter region and methotrexate metabolism in adult acute lymphoblastic leukemia.

Aims: To analyze the methylation level in the promoter region of SLC19A1 in adult acute lymphoblastic leukemia (ALL) patients, and explore the relationship between methotrexate (MTX) drug metabolism and SLC19A1 methylation. Methods: The methylation levels of the SLC19A1 promoter region in 52 adult ALL patients who received high-dose MTX chemotherapy were retrospectively analyzed in combination with clinical indicators and plasma MTX concentration. Results: Methylation levels of 17 CpG units were differently correlated with clinical parameters of ALL patients including gender, age, immunophenotype and Philadelphia chromosome status. Patients with delayed MTX drug excretion had higher methylation levels in the SLC19A1 promoter region. Conclusion: The methylation may affect the MTX plasma level and adverse reactions, which may predict patients at risk of adverse reactions after high-dose MTX therapy.

Optimal Administration of Glycyrrhizin Avoids Pharmacokinetic Interactions With High-dose Methotrexate and Exerts a Hepatoprotective Effect.

Glycyrrhizin (GZ) is widely used to treat high-dose methotrexate (MTX)-induced liver dysfunction. However, in a previous in vivo study, we showed that simultaneous administration of both drugs increased the plasma concentration of MTX and exacerbated hepatic injuries. In this study, we investigated the optimal dosing interval in rats to avoid the interaction between high-dose MTX and GZ and to demonstrate the inherent hepatoprotective effect of GZ. Male Wistar rats were treated with high-dose MTX (2,000 mg/kg) alone, with concomitant administration of 100 mg/kg GZ or GZ administered 3, 6, and 24 h before MTX administration. Plasma concentrations of MTX, alanine aminotransferase, aspartate aminotransferase, and total bilirubin were measured. The plasma concentration and half-life of methotrexate were significantly increased after concomitant administration of GZ, or when GZ was administered 3 h before MTX administration, compared with MTX alone, increasing hepatic enzyme levels. However, when GZ was administered 6 and 24 h before MTX administration, the levels were not significantly different from those of MTX alone and showed a tendency to decrease MTX-induced liver injury. These results suggest that the pharmacokinetic interaction between GZ and MTX could be avoided and the hepatoprotective effect of GZ could be achieved by an optimal dosing regimen, using the half-life of GZ as an indicator. When using high-dose MTX in combination with GZ, the administration intervals should be considered to avoid unwanted interactions and to achieve the GZ hepatoprotective effect.

Relationship between MTHFR Gene Polymorphism(C677T) and Adverse Reactions of High-Dose Methotrexate in Pediatric Patients with Acute Lymphoblastic Leukemia

To explore the effects of methylenetetrahydrofolate reductase (MTHFR) C677T gene polymorphism on the adverse reactions of high-dose methotrexate (MTX) in pediatric patients with acute lymphoblastic leukemia (ALL). A total of 69 children with ALL admitted to the department of Pediatrics of Sun Yat-sen Memorial Hospital of Sun Yat-sen University from November 2018 to October 2020 were included in this study. The clinical data of the children were collected, leukocytes were isolated from their peripheral blood, and MTHFR genotyping was performed by digital fluorescence molecular hybridization techniques. The adverse reactions and plasma drug concentration of MTX were monitored during the chemotherapy. Moreover, the effect of MTHFR gene polymorphism on MTX adverse reactions and plasma drug concentration were analyzed. Among the middle and high risk children, compared with the wildtype group (CC genotype), patients with MTHFR C677T mutations (CT+TT genotypes) had a higher risk of leukopenia (OR=2.38), neutropenia (OR=2.2), anemia (OR=1.83) and hepatoxicity (OR=1.98). However, no significant difference was found in the MTX plasma concentration between the MTHFR C677T mutantion group and the wildtype group at different timepoints (24 h, 48 h and 72 h). Multivariate analysis revealed that the plasma concentration of MTX (48 h), clinical risk level of ALL and MTHFR C677T gene polymorphism were independent factors for the adverse reactions of high-dose MTX. The MTHFR C677T mutations may be associated with myelosuppression and hepatotoxicity in children with ALL after high-dose MTX treatment.

Development of a population pharmacokinetics and pharmacodynamics model of glucarpidase rescue treatment after high-dose methotrexate therapy.

Glucarpidase (CPG2) reduces the lethal toxicity of methotrexate (MTX) by rapid degradation. In this study, a CPG2 population pharmacokinetics (popPK) analysis in healthy volunteers (phase 1 study) and a popPK-pharmacodynamics (popPK-PD) analysis in patients (phase 2 study, n = 15) who received 50 U/kg of CPG2 rescue for delayed MTX excretion were conducted. In the phase 2 study, the first CPG2 treatment at a dose of 50 U/kg was intravenously administered for 5min within 12h after the first confirmation of delayed MTX excretion. The second dose of CPG2, with a plasma MTX concentration >1 μmol/L, was administered to the patient more than 46h after the start of CPG2 administration. The population mean PK parameters (95% CI) of MTX, obtained from the final model post hoc, were estimated as follows: CLrMTX = 2.424 L/h (95% CI: 1.755-3.093), VcMTX = 12.6 L (95% CI: 10.8-14.3), VpMTX = 2.15 L (95% CI: 1.60-2.70), and α = 8.131 x 105 (4.864 x 105-11.398 x 105). The final model, including covariates, was CLrMTX (L/h): 3.248 x Body Weight/Serum creatinine/60 (CV 33.5%), VcMTX (L): 0.386 x Body Weight/body surface area (CV 29.1%), VpMTX (L):3.052 x Body Weight/60 (CV 90.6%), and α (L/h): 6.545 x 105 (CV 79.8%). These results suggest that the pre-CPG2 dose and 24h after CPG2 dosing were the most important sampling points in the Bayesian estimation of plasma MTX concentration prediction at 48h. These CPG2-MTX popPK analysis and Bayesian estimation of rebound in plasma MTX concentrations are clinically important to estimate >1.0 μmol/L 48h after the first CPG2 dosing. https://dbcentre3.jmacct.med.or.jp/JMACTR/App/JMACTRS06/JMACTRS06.aspx?seqno=2363, identifier JMA-IIA00078 and https://dbcentre3.jmacct.med.or.jp/JMACTR/App/JMACTRS06/JMACTRS06.aspx?seqno=2782, identifier JMA-IIA00097.

Magnetic Molecularly Imprinted Polymers for the Rapid and Selective Extraction and Detection of Methotrexatein Serum by HPLC-UV Analysis.

In this work, novel selective recognition materials, namely magnetic molecularly imprinted polymers (MMIPs), were prepared. The recognition materials were used as pretreatment materials for magnetic molecularly imprinted solid-phase extraction (MSPE) to achieve the efficient adsorption, selective recognition, and rapid magnetic separation of methotrexate (MTX) in the patients’ plasma. This method was combined with high-performance liquid chromatography–ultraviolet detection (HPLC–UV) to achieve accurate and rapid detection of the plasma MTX concentration, providing a new method for the clinical detection and monitoring of the MTX concentration. The MMIPs for the selective adsorption of MTX were prepared by the sol–gel method. The materials were characterized by transmission electron microscopy, Fourier transform-infrared spectrometry, X-ray diffractometry, and X-ray photoelectron spectrometry. The MTX adsorption properties of the MMIPs were evaluated using static, dynamic, and selective adsorption experiments. On this basis, the extraction conditions were optimized systematically. The adsorption capacity of MMIPs for MTX was 39.56 mgg−1, the imprinting factor was 9.40, and the adsorption equilibrium time was 60 min. The optimal extraction conditions were as follows: the amount of MMIP was 100 mg, the loading time was 120 min, the leachate was 8:2 (v/v) water–methanol, the eluent was 4:1 (v/v) methanol–acetic acid, and the elution time was 60 min. MTX was linear in the range of 0.00005–0.25 mg mL−1, and the detection limit was 12.51 ng mL−1. The accuracy of the MSPE–HPLC–UV method for MTX detection was excellent, and the result was consistent with that of a drug concentration analyzer.

Xanthones from securidaca inappendiculata antagonizes the anti-rheumatic effect of methotrexate by inhibiting reduced folate carrier 1

Background The first-line anti-rheumatic drug methotrexate (MTX) is used in the combination. Because of the unpredictable adverse reactions, optimization of relevant regimens is necessary and meaningful. This study aimed to study the possible interaction between Securidaca inappendiculate Hassk. Derived xanthones and MTX. Methods We established adjuvant-induced arthritis (AIA) model, which was treated with MTX and MTX + xanthone-rich fraction (XRF). The clinical efficacy was evaluated by histopathological examination, and LC-MS was used to monitor the blood concentration of MTX. Western blotting and immunohistochemistry were used to detect protein expression. In vitro, we assessed the activity of related transporters by cellular uptake assay based on HEK-293T cells. Results Compared with MTX-treated rats, inflammation in the immunized rats in the MTX + XRF group was obvious, indicating that XRF antagonized the anti-rheumatic effect of MTX. Meanwhile, XRF reduced liver and kidney injuries caused by MTX in addition to MTX. Results from immunohistochemical and nappendiculat assays suggested that XRF may reduce uptake of MTX by down-regulating reduced folate carrier 1 (RFC1). Conclusion This study indicated that XRF could reduce the plasma concentration of MTX by inhibiting the expression of RFC1, antagonize the therapeutic effect of MTX on AIA rats, and reduce its oral bioavailability. The combination of S. inappendiculate and MTX should be further optimized to achieve the goal of increasing efficiency and reducing toxicity.

Glycolysis aggravates methotrexate toxicity by fueling RFC1-controlled intestinal absorption in rheumatic rats.

Methotrexate (MTX) is a first line anti-rheumatic drug. This study was designed to investigate the impact of rheumatoid arthritis (RA) conditions on its oral absorption, and clarify the relevance with changes of MTX absorption-related transporters in rheumatic models. MTX was orally administered to healthy, collagen-induced arthritis (CIA), and adjuvant-induced arthritis (AIA) rats. MTX plasma concentrations were determined by a validated liquid chromatography-mass spectrometry method. We found that intestinal MTX absorption was significantly increased in CIA/AIA rats versus healthy controls. This finding was supported by small intestine-based MTX uptake assay in vitro. Meanwhile, intestinal expression of both reduced folate carrier 1 (RCF1) and proton-coupled folate transporter (PCFT) remained unchanged. The everted intestinal sac assay confirms RFC1 is the key transporter accounting for intestinal MTX absorption, as its antagonist salicylazosulfapyridine showed potent capacity in reducing MTX uptake. No correlation between RA-related cytokines and RCF1 expression was observed in clinical samples. We further revealed that when cultured with AIA rat or RA patient serum, lactate and adenosine triphosphate (ATP) production as well as MTX uptake in MDCKII cells were significantly increased, and this increase was completely abrogated by ATP production-related metabolic inhibitors. Thanks to its inhibitory effects on MTX bioavailability, the glycolysis inhibitor shikonin diminished MTX-induced injuries of kidney and liver in AIA rats. These data demonstrate that glycolysis-driven high energy metabolism increases MTX absorption in rheumatic subjects, leading to the exacerbated toxicity. These findings will have important implications in optimizing MTX regimens for RA treatment with better efficacy and lower toxicity.

Validation of a simple HPLC method to quantify methotrexate concentrations in human plasma

Methotrexate (MTX) is a chemotherapy and immunosuppressive agent widely used to treat cancer, autoimmune diseases in children and adult patients, and ectopic pregnancy. However, MTX is highly toxic to the liver, kidney, and nervous system. This study aimed to quantify the concentration of MTX in human plasma using high-performance liquid chromatography (HPLC). MTX and its internal standard (para aminoacetophenone-PAPA) in plasma samples were extracted simultaneously with methanol. Sample purity was performed using the 1 cc OASIS HLB cartridges. Sample injection volume of 10 μL was analyzed on a Lichrocart Supersil 125-4 column C18 maintained at 40 °C on a Waters 2695 XE equipped with a PDA detector set at 303 nm. The mobile phase contained phosphate buffer (pH 6.0) and methanol at a ratio of 80:20 (v/v) and was maintained at a flow rate of 1 ml/min. The results showed that the total time of chromatographic analysis was 15 min. MTX and PAAP were found in the chromatograms at retention times of 2.3 and 5.2 min, respectively. The linear range of the MTX from 0.5 to 25 μg/mL. Intra-day and inter-day imprecision for MTX ranged from 3.42 to 8.128%. LLOQ of MTX was 0.5 μg/mL and the extraction effects were above 77%. In conclusion, we developed and validated a simple HPLC method to determine the MTX concentrations in human plasma.

Evaluation and Application of Population Pharmacokinetic Models for Identifying Delayed Methotrexate Elimination in Patients With Primary Central Nervous System Lymphoma

Objective: Several population pharmacokinetic (popPK) models have been developed to determine the sources of methotrexate (MTX) PK variability. It remains unknown if these published models are precise enough for use or if a new model needs to be built. The aims of this study were to 1) assess the predictability of published models and 2) analyze the potential risk factors for delayed MTX elimination. Methods: A total of 1458 MTX plasma concentrations, including 377 courses (1–17 per patient), were collected from 77 patients who were receiving high-dose MTX for the treatment of primary central nervous system lymphoma in Huashan Hospital. PopPK analysis was performed using the NONMEM® software package. Previously published popPK models were selected and rebuilt. A new popPK model was then constructed to screen potential covariates using a stepwise approach. The covariates were included based on the combination of theoretical mechanisms and data properties. Goodness-of-fit plots, bootstrap, and prediction- and simulation-based diagnostics were used to determine the stability and predictive performance of both the published and newly built models. Monte Carlo simulations were conducted to qualify the influence of risk factors on the incidence of delayed elimination. Results: Among the eight evaluated published models, none presented acceptable values of bias or inaccuracy. A two-compartment model was employed in the newly built model to describe the PK of MTX. The estimated mean clearance (CL/F) was 4.91 L h−1 (relative standard error: 3.7%). Creatinine clearance, albumin, and age were identified as covariates of MTX CL/F. The median and median absolute prediction errors of the final model were -10.2 and 36.4%, respectively. Results of goodness-of-fit plots, bootstrap, and prediction-corrected visual predictive checks indicated the high predictability of the final model. Conclusions: Current published models are not sufficiently reliable for cross-center use. The elderly patients and those with renal dysfunction, hypoalbuminemia are at higher risk of delayed elimination.

Predictors of Chemotherapy Induced Adverse Events in Pediatric Osteosarcoma Patients.

Objective:To investigate the prevalence of chemotherapy-induced adverse events and the associated risk factors in pediatric patients with osteosarcoma. Methods:This retrospective cross-sectional study enrolled 90 pediatric osteosarcoma patients (with 1,017 chemotherapy cycles) treated at Srinagarind Medical Center, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand, between January 1, 2008 and December 31, 2018. The prevalence of major adverse events and a correlation between baseline characteristics and adverse events were analyzed using a generalized estimating equation model. Result:The prevalence of adverse events in 90 pediatric osteosarcoma patients (with 1,017 chemotherapy cycles) was determined as chemotherapy-induced nausea and vomiting (29.2%; n=296), hepatotoxicity (21.2%; n=215), anemia (70.69%; n=719), neutropenia (26.65%; n=271), and thrombocytopenia (13.65%; n=139). Factors associated with chemotherapy-induced hepatotoxicity included methotrexate dose ≥ 12 g/m2 (odds ratio [OR] 1.30; 95% confidence interval [CI] 1.22–1.39; P<0.001), plasma concentration of methotrexate at 72 hours >0.1 μM (OR 1.22; 95% CI 1.19–1.25; P<0.001), and pre-hydration rate ≤ 125 mL/m2/h (OR 1.10; 95% CI 1.07–1.12; P<0.001). Conclusion:Major adverse events are becoming more common in pediatric osteosarcoma patients, and risk factors include larger chemotherapy doses, higher plasma methotrexate concentrations, and a slower pre-hydration rate. The outcomes of the study could aid in the better treatment of toxicity in children with osteosarcoma.

Evaluation of body-surface-area adjusted dosing of high-dose methotrexate by population pharmacokinetics in a large cohort of cancer patients

BackgroundThe aim of this study was to identify sources of variability including patient gender and body surface area (BSA) in pharmacokinetic (PK) exposure for high-dose methotrexate (MTX) continuous infusion in a large cohort of patients with hematological and solid malignancies.MethodsWe conducted a retrospective PK analysis of MTX plasma concentration data from hematological/oncological patients treated at the University Hospital of Cologne between 2005 and 2018. Nonlinear mixed effects modeling was performed. Covariate data on patient demographics and clinical chemistry parameters was incorporated to assess relationships with PK parameters. Simulations were conducted to compare exposure and probability of target attainment (PTA) under BSA adjusted, flat and stratified dosing regimens.ResultsPlasma concentration over time data (2182 measurements) from therapeutic drug monitoring from 229 patients was available. PK of MTX were best described by a three-compartment model. Values for clearance (CL) of 4.33 [2.95–5.92] L h− 1 and central volume of distribution of 4.29 [1.81–7.33] L were estimated. An inter-occasion variability of 23.1% (coefficient of variation) and an inter-individual variability of 29.7% were associated to CL, which was 16 [7–25] % lower in women. Serum creatinine, patient age, sex and BSA were significantly related to CL of MTX. Simulations suggested that differences in PTA between flat and BSA-based dosing were marginal, with stratified dosing performing best overall.ConclusionA dosing scheme with doses stratified across BSA quartiles is suggested to optimize target exposure attainment. Influence of patient sex on CL of MTX is present but small in magnitude.

Downregulation of Renal MRPs Transporters in Acute Lymphoblastic Leukemia Mediated by the IL-6/STAT3/PXR Signaling Pathway.

PurposeConsidering prior investigations on reductions of renal multidrug resistance-associated protein (MRP) 2 and 4 transporters in mice with acute lymphoblastic leukemia (ALL), we sought to characterize the underlying mechanisms responsible for IL-6/STAT3/PXR-mediated changes in the expression of MRP2 and MRP4 in ALL.Subjects and MethodsALL xenograft models were established and intravenously injected with methotrexate (MTX) of MRPs substrate in NOD/SCID mice. Protein expression of MRPs and associated mechanisms were detected by Western blotting and immunocytochemistry. Plasma concentrations of MTX were determined using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS).ResultsPlasma IL-6 levels in patients with newly diagnosed ALL were increased compared to children with pneumonia. Similarly, plasma IL-6 levels in ALL, ALL-tocilizumab (TCZ, an IL-6 receptor inhibitor) and ALL-S3I-201 (a selective inhibitor of STAT3) mice were increased compared to the control group. The MRP2, MRP4, and PXR expression in HK-2 cells treated with IL-6 were decreased, whereas the p-STAT3 expression was significantly increased compared to the control group results. These results are consistent with clearance of MRPs-mediated MTX in the ALL group. These effects were attenuated by blocking IL-6/STAT3/PXR signaling pathway.ConclusionInflammation-mediated changes in pharmacokinetics are thought to be executed through pathways IL-6-activated pathways, which can facilitate a better understanding of the potential for the use of IL-6 to predict the severity of adverse outcomes and the major implications on potential ALL treatments.

Relationship Between the Free and Total Methotrexate Plasma Concentration in Children and Application to Predict the Toxicity of HD-MTX.

High-dose methotrexate (HD-MTX) can be highly effective as well as extremely toxic. Many drug molecules can bind to plasma proteins to different extents in vivo, whereas only the free drug can reach the site of action to exert a pharmacological effect and cause toxicity. However, free MTX concentrations in plasma have not been reported. Traditional analyses of free drugs are both cumbersome and inaccurate. We collected 92 plasma samples from 52 children diagnosed with ALL or NHL or other lymphomas that were treated with HD-MTX. The hollow fiber centrifugal ultrafiltration (HFCF-UF) was used to prepare plasma samples for analysis of the free MTX concentration. Protein precipitation was employed to measure the total MTX concentration. The HFCF-UF is a simple method involving a step of ordinary centrifugation; the validation parameters for the methodological results were satisfactory and fell within the acceptance criteria. A linearity coefficient r 2 of 0.910 was obtained for the correlation between the free and total MTX plasma concentrations in 92 plasma samples. However, the free and total MTX concentrations was only weakly correlated in 16 clinical plasma specimens with total MTX concentrations >2 μmol L−1 (r 2 = 0.760). Both the free and total MTX concentrations at 42 h were negatively correlated with the creatinine clearance (CCr) level (P = 0.023, r = −0.236 for total MTX and P = 0.020, r = −0.241for free MTX, respectively). The free MTX concentration could not be accurately estimated from the total MTX concentration for patients with high MTX levels which are conditions under which toxic reactions are more likely to occur. High plasma MTX levels could become a predictor of the occurrence of MTX nephrotoxicity to draw people's attention. The proposed HFCF-UF method is a simple and accurate way to evaluate efficacy and toxicity in clinical therapeutic drug monitoring.

Effect of Body Fat on Population Pharmacokinetics of High-Dose Methotrexate in Pediatric Patients With Acute Lymphoblastic Leukemia.

Nearly all international regimens for pediatric acute lymphoblastic leukemia (ALL) incorporate intravenous "high-dose" methotrexate (HDMTX, ≥1g/m2 ) to penetrate the central nervous system. Dosing is routinely adjusted for body surface area (BSA), but limited data describe the pharmacokinetics of HDMTX, particularly in obese and/or large patients. To understand the impact of body size (BSA) and body fat percentage (BFP) on HDMTX pharmacokinetics, we performed a secondary analysis of 36 children and adolescents 10-21 years old treated for newly diagnosed ALL and who were enrolled in a prospective study examining body composition. All patients received 5 g/m2 of HDMTX infused over 24 hours. Plasma methotrexate concentrations were measured at 24, 42, and 48 hours. At 48 hours, ≥0.4 μmol/L was defined as "delayed elimination," necessitating prolonged supportive care. BFP was measured using dual-energy x-ray absorptiometry. A nonparametric population pharmacokinetic model was constructed with subsequent simulations to explore effects of BSA and BFP extremes. Despite standard BSA-adjusted dosing, we found significant intrapatient variability in mean MTX concentration (38%; range, 1.2%-86%). BSA and BFP were not linearly associated with increased area under the curve (AUC, P = 0.74 and P = 0.12), but both larger size (BSA) and greater obesity (BFP) were associated with an approximately 2-fold higher risk for delayed elimination at 48 hours. HDMTX AUC was not associated with toxicity. MTX pharmacokinetics vary among and even within patients despite BSA-adjusted dosing. Obesity and large size are identified as new risk factors for delayed elimination, requiring further investigation.

The increasing doses of methotrexate pharmacokinetics after intravenous administration in rats - model selection

Background/Aim. Methotrexate (MTX) plays a significant role in the treatment of various diseases, but the toxicity remains the main issue of its use, especially when administered in high doses. Considering altered pharmacokinetics of MTX as a factor strongly implicated in the large interpatient variability and unexpected toxicity in certain patients, the accurate description of MTX pharmacokinetic behaviour of both low and high doses is of the utmost importance. Therefore, the objective of this study was to determine the pharmacokinetics of MTX after intravenous (iv) administration in ascending doses of 5, 40, 80 and 160 mg/kg in rats and to select the appropriate mathematical model describing MTX pharmacokinetics. Methods. Plasma concentrations of MTX were measured using the liquid chromatography - mass spectrometry (LC/MS) method. Pharmacokinetic parameters were calculated by non-compartmental and two-compartmental integer-order analyses. Results. MTX showed linear pharmacokinetics following iv administration up to the dose of 80 mg/kg. The administration of a high dose of MTX (160 mg/kg) resulted in the similar pharmacokinetic behaviour as when applied in the twice lower dose (80 mg/kg), which can be explained by dose-dependent changes in the expression of solute carrier (SLC) and ATP binding cassette (ABC) transport proteins and intracellular metabolism. Furthermore, the classical two-compartment model could not explain the pharmacokinetics of MTX in a small percentage of experimental animals, which opens up new strategies for the use of fractional order pharmacokinetic models in MTX therapy optimisation. Conclusion. These results of pharmacokinetic analyses may be helpful in adjusting the dosage regimen of MTX, but the application of novel pharmacokinetic models, such as those based on fractional calculus, is still needed in the process of MTX therapy optimisation.

Concomitant Use of High-dose Methotrexate and Glycyrrhizin Affects Pharmacokinetics of Methotrexate, Resulting in Hepatic Toxicity.

High-dose methotrexate is a therapy for acute leukemia, malignant lymphoma, and osteosarcoma. Glycyrrhizin has been used to treat hepatic dysfunction caused by high-dose methotrexate. However, few studies have investigated the interaction between glycyrrhizin and high-dose methotrexate. Male Wistar rats were treated with high-dose methotrexate (500 or 1,000 mg/kg) alone, or with co-administration of 100 mg/kg glycyrrhizin. Plasma concentrations of methotrexate, alanine aminotransferase, aspartate aminotransferase, and total bilirubin were measured. At both methotrexate doses, the blood concentration of methotrexate was significantly increased and total clearance was significantly reduced using co-administration of glycyrrhizin compared with methotrexate alone, which led to increased levels of hepatic enzymes. These results suggest that glycyrrhizin significantly increases the plasma level and delays the clearance of methotrexate, resulting in hepatic toxicity. The concomitant use of methotrexate and glycyrrhizin should be considered with caution.

Development and Validation of a High-Performance Liquid Chromatography–Tandem Mass Spectrometry Method for Methotrexate Quantitation in Human Serum

Methotrexate (MTX) is the only chemotherapy drug that is routinely monitored by therapeutic drug monitoring service in Malaysia government hospitals. The patients with MTX plasma concentration exceeding 0.4 μM for 48 h are at higher risk to develop toxicities such as nephrotoxicity, hepatotoxicity, neurotoxicity, mucositis and myelosuppression. The aim of this study was to develop and validate the ultra-high performance liquid chromatography−tandem mass spectrometry (UHPLC−MS/MS) method for MTX quantitation in human serum. Our results show that the retention times of MTX and warfarin (internal standard) were 1.82 and 2.68 min, respectively. The linearity was obtained at the concentrations from 25 to 500 ng/mL with the regression equation of y = 1025x – 11757 and r2 of 0.9901. This analyte was stable in a freezer at –80°C for up to 90 days. As a conclusion, this UHPLC−MS/MS method is an optional technique for clinicians to quantitate the patient’s MTX levels in the hospital.