Determination of methotrexate and 7-hydroxymethotrexate by liquid chromatography for routine monitoring of plasma levels

Facile Electrochemical Determination of Methotrexate (MTX) Using Glassy Carbon Electrode-Modified with Electronically Disordered NiO Nanostructures

Recently, the oxidative behavior of methotrexate (MTX) anticancer drug is highly demanded, due to its side effects on healthy cells, despite being a very challenging task. In this study, we have prepared porous NiO material using sodium sulfate as an electronic disorder reagent by hydrothermal method and found it highly sensitive and selective for the oxidation of MTX. The synthesized NiO nanostructures were characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD) techniques. These physical characterizations delineated the porous morphology and cubic crystalline phase of NiO. Different electrochemical approaches have been utilized to determine the MTX concentrations in 0.04 M Britton-Robinson buffer (BRB) at pH 2 using glassy carbon electrode (GCE)-modified with electronically disordered NiO nanostructures. The linear range for MTX using cyclic voltammetry (CV) was found to be from 5 to 30 nM, and the limit of detection (LOD) and limit of quantification (LOQ) were 1.46 nM and 4.86 nM, respectively, whereas the linear range obtained via linear sweep voltammetry (LSV) was estimated as 15-90 nM with LOD and LOQ of 0.819 nM and 2.713 nM, respectively. Additionally, amperometric studies revealed a linear range from 10 to70 nM with LOD and LOQ of 0.1 nM and 1.3 nM, respectively. Importantly, MTX was successfully monitored in pharmaceutical products using the standard recovery method. Thus, the proposed approach for the synthesis of active metal oxide materials could be sued for the determination of other anticancer drugs in real samples and other biomedical applications.

Comparison of four immunoassays to an HPLC method for the therapeutic drug monitoring of methotrexate: Influence of the hydroxylated metabolite levels and impact on clinical threshold

OBJECTIVES

Methotrexate requires therapeutic drug monitoring in oncology because of narrow therapeutic index, especially the metabolite 7-hydroxymethotrexate exhibits nephrotoxicity. The goal of this study was to evaluate different assays and their impact on clinical decisions.

METHODS

Following routine measurement with Abbott TDxFLx® assay (MTX-TDX), 62 samples were analysed on Architect®i1000 (MTX-ARCHI), Xpand® (ARK/XPND), Indiko® (ARK/INDI), and HPLC (MTX-HPLC) as the reference method. The influence of 7-hydroxymethotrexate was explored on ARK reagent to document the cause of the observed bias. ROC curves were built to study the impact of the method on the discharge thresholds for the patients at three levels.

RESULTS

Total imprecision was below 2.60% for the methotrexate-ARCHI and close to 10% for both ARK assays for plasma pools. The correlation coefficients were 0.93, 0.93, 0.89 and 0.95, the Bland-Altman difference plot revealed a bias of 0.075, 0.037, 0.049 and -0.002, and the number of results exceeding the TE criteria of 0.1 µM was 17 (27%), 13 (21%), 15 (24%) and 15 (24%) for MTX-TDX, ARK/INDI, ARK/XPND and MTX-ARCHI, respectively. Cross reactivity with 7-hydroxymethotrexate was between 1 and 9%. Overestimation of methotrexate concentration was between -4% and +32%. The most robust clinical level was found to be the highest level (0.2 µM) with ROC curves.

CONCLUSIONS

The authors found the best results for imprecision with chemiluminescent microparticle immunoassay method on methotrexate-ARCHI, with bias below to the RICOS recommendations and best correlation to the reference method. Impact on the threshold values for clinical decision need to be clearly exposed to clinicians.

A sensitive electrochemical determination of chemotherapy agent using graphitic carbon nitride covered vanadium oxide nanocomposite; sonochemical approach

We have developed a graphitic carbon nitride covered vanadium oxide nanocomposite (V₂O₅@g-C₃N₄) by a simple sonochemical approach (50 kHz and 150 W/cm²). Furthermore, the morphology and chemical composition of the V₂O₅@g-C₃N₄ nanocomposite was carried out by X-rays diffractometry (XRD), transmission electron microscopy (TEM) and electrochemical impedance spectroscopy (EIS). Furthermore, the V₂O₅@g-C₃N₄ nanocomposite modified electrode was investigate electrochemical behavior of the anticancer drug. Compared with bare SPCE, V₂O₅/SPCE and g-C₃N₄/SPCE, V₂O₅@g-C₃N₄ modified SPCE showed highest current response towards anti-cancer drug (methotrexate). Furthermore, the modified sensor exhibits with a sharp peaks and wide linear range (0.025-273.15 μM) by using DPV with the sensitivity of 7.122 μA μM^-1 cm^-2. Notably, we have achieved a nanomolar detection limit (13.26 nM) for the DPV detection of methotrexate. Further, the practicability of the V₂O₅@g-C₃N₄ nanocomposite modified sensor can be used for real time sensing of methotrexate in drug and blood serum samples with good recover ranges. It has potential applications in routine analysis with high specificity, excellent reproducibility and good stability.

Optimized high performance liquid chromatography-ultraviolet detection method using core-shell particles for the therapeutic monitoring of methotrexate

Methotrexate (MTX) is an antineoplastic drug, and due to its high toxicity, the therapeutic drug monitoring is strictly conducted in the clinical practice. The chemometric optimization and validation of a high performance liquid chromatography (HPLC) method using core-shell particles is presented for the determination of MTX in plasma during therapeutic monitoring. Experimental design and response surface methodology (RSM) were applied for the optimization of the chromatographic system and the analyte extraction step. A Poroshell 120 EC-C18 (3.0 mm×75 mm, 2.7 μm) column was used to obtain a fast and efficient separation in a complete run time of 4 min. The optimum conditions for the chromatographic system resulted in a mobile phase consisting of acetic acid/sodium acetate buffer solution (85.0 mM, pH=4.00) and 11.2% of acetonitrile at a flow rate of 0.4 mL/min. Selectivity, linearity, accuracy and precision were demonstrated in a range of 0.10-6.0 µM of MTX. The application of the optimized method required only 150 µL of patient plasma and a low consumption of solvent to provide rapid results.

Ultrafast selective quantification of methotrexate in human plasma by high-throughput MALDI-isotope dilution mass spectrometry

BACKGROUND

A new analytical MS method using isotope dilution combined with MALDI-triple quadrupole MS/MS has been developed and validated for the determination of methotrexate and 7-hydroxymethotrexate in plasma. Methotrexate, methotrexate-d3, 7-hydroxymethotrexate and 7-hydroxymethotrexate-d3 were monitored by selected reaction monitoring using the transitions m/z 455.2→308.2, 458.2→311.2, 471.2→324.2 and 474.2→327.2 for methotrexate, methotrexate-d3, 7-hydroxymethotrexate and 7-hydroxymethotrexate-d3, respectively.

RESULTS

The LLOQ was 1 nmol/l for methotrexate and 7-hydroxymethotrexate while the limit of detection was 0.3 nmol/l for both analytes. The new developed method was cross-validated by a fluorescence polarization immunoassay and tested for its clinical feasibility by measuring plasma samples from patients suffering from acute lymphoblastic leukemia. Plasma methotrexate concentrations ranged between 66.0 and 954 nmol/l and observed 7-hydroxymethotrexate/methotrexate ratios ranged between 0.1 and 32.4, respectively.

CONCLUSION

The new method showed comparable analytical performances as the fluorescence polarization immunoassay, but analyte specificity and sensitivity of the newly developed method were significantly better.

Novel integrin-targeted binding-triggered drug delivery system for methotrexate

PURPOSE

To design a binding-induced conformation change drug delivery system for integrin-targeted delivery of methotrexate and prove the feasibility of using hairpin peptide structure for binding triggered drug delivery.

METHODS

Methotrexate prodrugs were synthesized using solid phase peptide synthesis techniques by conjugating methotrexate to Arg-Gly-Asp (RGD) or a hairpin peptide, RWQYV(D)PGKFTVQRGD (hairpin-RGD). Levels of integrin α(V)β(3) in HUVEC were up-regulated using adenoviral system and knocked down using siRNA. Stability of prodrugs and methotrexate release from prodrugs were evaluated in plasma, in presence or absence of integrin α(V)β(3)-expressing cells. Molecular modeling was performed to support experimental results using MOE.

RESULTS

Prodrugs recognized and bound to integrin α(V)β(3)-expressing cells in integrin α(V)β(3) expression level-dependent manner. Prodrug with hairpin peptide could resist Streptomyces griseus-derived glutamic acid-specific endopeptidase (SGPE) and plasma enzyme hydrolysis. Drug release was triggered in presence of HUVEC cells and SGPE. Analysis of conformation energy supported that conformational change in MTX-hairpin-RGD led to exposure of labile link upon binding to integrin α(V)β(3)-expressing cells.

CONCLUSIONS

Binding-induced conformation change of hairpin peptide can be used to design integrin-targeted drug delivery system.

Synergistic effect of iontophoresis and soluble microneedles for transdermal delivery of methotrexate

The aim of this study was to investigate the transdermal iontophoretic delivery of methotrexate, alone or in combination with microneedles, in-vitro and in-vivo using intracutaneous microdialysis in the hairless rat. The average depth of the microdialysis probe in the skin was found to be 0.54 mm. Methotrexate was stable in the presence of an applied electric field as determined by cyclic voltammetry. A current density of 0.4 mA cm−2 applied for 60 min was used in combination with maltose microneedles to enhance delivery of methotrexate across the skin. Delivery was enhanced by iontophoresis and microneedles, both in-vitro and in-vivo. A synergistic 25-fold enhancement of delivery was observed in-vivo when a combination of microneedles and iontophoresis was used compared with either modality alone.

Monoketocholate can decrease transcellular permeation of methotrexate across Caco-2 cell monolayers and reduce its intestinal absorption in rat

Objectives

Bile salts have been shown to decrease the absorption of methotrexate in the rat intestine by an unknown mechanism. We aimed to examine this effect.

Methods

We assessed apical-to-basolateral (AP-BL) permeation of methotrexate (5 μM) across Caco-2 cell monolayers pretreated with various concentrations (0, 0.25, 0.5, 1, 3 and 5 mm) of sodium cholate or its semisynthetic analogue, sodium 12-monoketocholate. We also determined the effect of orally administered 12-monoketocholate on the intestinal absorption of methotrexate in rats to evaluate a possible in-vitro–in-vivo correlation.

Key findings

It was found that sodium cholate and sodium 12-monoketocholate decreased the AP-BL permeation of methotrexate at low concentrations (maximal inhibition at 0.25 and 1 mm, respectively) and increased it at higher concentrations. Determination of [14C] mannitol permeation and electrical resistance of monolayers during experiments showed that membrane integrity was not compromised at low concentrations of bile salts but was disrupted at higher concentrations. Subsequently, we examined the effect of the simultaneous oral administration of sodium 12-monoketocholate (4, 20, 40 and 80 mg/kg) on the intestinal absorption of methotrexate in rats after an oral dose (5 mg/kg). The pharmacokinetic study showed that 12-monoketocholate at 4 and 20 mg/kg did not change the methotrexate area under the serum concentration–time curve whereas sodium 12-monoketocholate at 40 and 80 mg/kg significantly reduced it.

Conclusions

Sodium 12-monoketocholate appears to decrease the intestinal absorption of methotrexate in rats by inhibition of transcellular active transport.

Determination of methotrexate and its major metabolite 7-hydroxymethotrexate in mouse plasma and brain tissue by liquid chromatography-tandem mass spectrometry

Methotrexate (MTX) is an anticancer agent that is widely used in a variety of human cancers including primary central nervous system lymphoma (PCNSL). Important pharmacological properties that directly bear on the use of MTX in PCNSL, such as mechanisms that govern its uptake into brain tumors, are poorly defined, but are amenable to investigation in mouse models. In order to pursue such preclinical pharmacological studies, a rapid and sensitive liquid chromatography-tandem mass spectrometry (LC/MS/MS) method for the determination of MTX and its metabolite, 7-hydroxymethotrexate (7-OH MTX) in plasma and microdialysate samples from brain tumors and cerebrospinal fluid (CSF) is needed. The plasma assay was based on 10 microl samples and following a protein precipitation procedure enabled direct injection onto a LC/MS/MS system using positive electrospray ionization. A column switching technique was employed for desalting and the clean-up of microdialysate samples from brain tissues. The methods were validated for MTX and 7-OH MTX in both plasma and microdialysate samples from brain tumor and CSF, and produced lower limits of quantification (LLOQ) in plasma of 3.7 ng/ml for MTX and 7.4 ng/ml for 7-OH MTX, and in microdialysate samples of 0.7 ng/ml for both MTX and 7-OH MTX. The utility of the method was demonstrated by estimation of pharmacokinetic (PK) and brain distribution properties of MTX and 7-OH MTX in conscious mice. The method has the advantages of low sample volume, rapid clean-up, and the simultaneous measurement of MTX and 7-OH MTX in plasma and brain tissues allowing detailed PK studies to be completed in individual mice.

Pharmacokinetic study of methotrexate following intra-articular injection of methotrexate loaded poly(L-lactic acid) microspheres in rabbits

The pharmacokinetics and tissue distribution of methotrexate (MTX) were investigated following intra-articular injection of either MTX solution or controlled release MTX loaded microspheres in healthy rabbit joints. MTX solution or MTX loaded microspheres (size 30-100 mum) (10 mg MTX) was injected into the right knee joint cavity of rabbits. Blood samples were taken at predetermined times from the jugular vein. Urine samples were also collected over time periods up to 24 h. The major organs and synovial tissues were removed for analysis 6 and 24 h post-injection (n = 4). MTX and 7-OH-MTX concentrations in the plasma and major organs were determined by HPLC. The MTX plasma area under the concentration-time curve (AUC) for rabbits injected with MTX solution was seven fold higher than that of the rabbits injected with MTX microspheres, while t(1/2) and mean residence time (MRT) were not significantly different between two treatment groups. Four fold more MTX was excreted in the urine from rabbits injected with MTX solution compared to those injected with MTX loaded microspheres 24 h following intra-articular injection. The concentration of MTX in the synovial tissues following intra-articular injection was significantly higher in the rabbits injected with microspheres than in the rabbits injected with MTX solution. MTX solution was rapidly cleared from the joint cavity while MTX encapsulated microspheres retained MTX in the joint cavity.

Methotrexate loaded poly(L-lactic acid) microspheres for intra-articular delivery of methotrexate to the joint

A controlled release delivery system that localizes methotrexate (MTX) in the synovial joint is needed to treat inflammation in rheumatoid arthritis (RA). The purpose of this work was to develop and characterize MTX loaded poly(l-lactic acid) (PLLA) microspheres and evaluate in vivo tolerability and MTX plasma concentrations following intra-articular injection into healthy rabbits. MTX loaded PLLA (2 kg/mole) microspheres were prepared using the solvent evaporation method and characterized in terms of size, molecular weight, thermal properties, and release rates into phosphate buffered saline (PBS) (pH 7.4) at 37 degrees C. Biocompatibility was evaluated by observing the swelling of the joints of the rabbits and histological analysis following the injection of the microspheres. MTX concentrations in the plasma and urine samples of rabbits were evaluated by high-performance liquid chromatography (HPLC). MTX loaded microspheres showed a rapid burst phase followed by a slow release phase. MTX loaded and control microspheres were biocompatible and plasma concentrations of MTX were tenfold higher in rabbits injected intra-articularly with free MTX than MTX microspheres. MTX microspheres may retain the drug in the joint by reducing clearance from the joint into the blood.

Optimal management of methotrexate intoxication in a child with osteosarcoma

OBJECTIVE

To describe the time course and management of methotrexate (MTX) toxicity in a 14-year-old Hispanic boy with osteosarcoma treated with high-dose MTX.

CASE SUMMARY

During the sixth cycle of high-dose MTX, severe intoxication was observed with high MTX plasma concentrations, acute renal failure, and hepatitis, followed by mucositis and moderate myelosuppression. Intensification of urine alkalinization and increased leucovorin dosages did not decrease plasma concentrations of MTX or prevent systemic toxicities. Carboxypeptidase G2 and aminophylline were thus administered as a second-intention rescue strategy. Within 2 weeks, a recovery of clinical symptoms and normalization of the biological abnormalities were observed. Limb salvage surgery was performed, which permitted classifying the patient as an MTX high-responder. Thereafter, MTX was successfully resumed, leading to clinical recovery of the patient. Concomitantly, homocysteine plasma levels, a marker of the pharmacodynamic effect of MTX, were measured. During the intoxication, homocysteine plasma levels were significantly increased, parallel to the excessive MTX plasma concentrations observed.

DISCUSSION

According to the excessive MTX levels measured in this patient, along with the observed clinical (mucositis) and biological (hepatitis, renal injury) adverse effects, we suggest that MTX may be a cause of these complications. Use of the Naranjo probability scale indicated a probable relationship between the complications and MTX.

CONCLUSIONS

This observation shows that severe complications observed during one cycle of high-dose MTX is not predictive of the tolerability of further courses. Optimal management of such complications, using specific therapeutic intervention, may be considered.

Pharmacokinetics of methotrexate in rabbit skin and plasma after iv-bolus and iontophoretic administrations

The pharmacokinetics of methotrexate (MTX) in rabbit's skin and plasma after iv-bolus and iontophoretic delivery at different current densities was studied. Linear microdialysis probes were introduced into the upper dorsal shaved skin of tranquilized rabbits. Commercially available patches were used to deliver MTX for 1 h at different current densities (100, 200, and 300 microA/cm2) on different occasions. Iv-boluses (10 mg/kg) of MTX were also administered. Retrodialysis was performed at the end of the experiments to estimate probe recovery. Plasma and microdialysis samples were analyzed using a validated HPLC assay. Following iv-bolus, MTX showed a bi-exponential decay both in plasma and in skin. Cmax in skin occurred with a delay of 22 min compared with plasma. No quantifiable concentration of MTX was detected in the skin on passive drug delivery. Systemic exposure to MTX (AUC) and Cmax increased linearly with current density. Nevertheless, exposure to MTX in the skin did not increase linearly with current density, whereas Cmax did. In conclusion, iontophoresis remarkably improved the dermal delivery of MTX over passive diffusion. However, total exposure did not increase with current density in the skin, suggesting that for local applications lower current densities may achieve the same effects with minimal systemic exposure.

Study of stability of methotrexate in acidic solution Spectrofluorimetric determination of methotrexate in pharmaceutical preparations through acid-catalyzed degradation reaction

Study of the degradation reaction of methotrexate (MTX) in acidic solution was carried out. Optimization of the experimental parameters of MTX acid hydrolysis was investigated. Spectrofluorimetric method for determination of MTX through measurement of its acid-degradation product, 4-amino-4-deoxy-10-methylpteroic acid (AMP), was developed. Stability of the standard solution of MTX prepared in sulfuric acid was discussed in the view of accelerated stability analysis. Two other comparative spectroflourimetric methods based on measuring the fluorescence intensities from either a condensation reaction with acetylacetone-formaldehyde (Hantzsch reaction) or a reaction with fluorescamine were also described. Beer's law validation, accuracy, precision, limits of detection, limits of quantification, and other aspects of analytical merit are presented in the text. The proposed methods were successfully applied for the analysis of MTX in pure drug and tablets dosage form. The sensitivity of the developed methods was favorable, so it was possible to be adopted for determination of MTX in plasma samples for routine use in high-dose MTX therapy.

Non-linear heteroscedastic regression model for determination of methotrexate in human plasma by high-performance liquid chromatography

Generalized least squares regression with variance function estimation was used to derive the calibration function for measurement of methotrexate plasma concentration and its results were compared with weighted least squares regression by usual weight factors and also with that of ordinary least squares method. In the calibration curve range of 0.05 to 100 microM, both heteroscedasticity and non-linearity were present therefore ordinary least squares linear regression methods could result in large errors in the calculation of methotrexate concentration. Generalized least squares regression with variance function estimation worked better than both the weighted regression with the usual weight factors and ordinary least squares regression and gave better estimates for methotrexate concentration.

Therapeutic isoniazid monitoring using a simple high-performance liquid chromatographic method with ultraviolet detection

Simultaneous measurement of isoniazid and its main acetylated metabolite acetylisoniazid in human plasma is realized by high-performance liquid chromatography. The technique used is evaluated by a factorial design of validation that proved to be convenient for routine drug monitoring. Plasma samples are deproteinized by trichloroacetic acid and then the analytes are separated on a microBondapak C18 column (Waters). Nicotinamide is used as an internal standard. The mobile phase is 0.05 M ammonium acetate buffer (pH 6)-acetonitrile (99:1, v/v). The detection is by ultraviolet absorbance at 275 nm. The validation, using the factorial design allows one to: (a) test the systematic factors of bias (linearity and matrix effect); (b) estimate the relative standard deviations (RSDs) related to extraction, measure and sessions assay. The linearity is confirmed to be within a range of 0.5 to 8 microg/ml of isoniazid and 1 to 16 microg/ml of acetylisoniazid. This method shows a good repeatability for both extraction and measurement (RSD INH=3.54% and 3.32%; RSD Ac.INH=0.00% and 5.97%), as well as a good intermediate precision (RSD INH=7.96%; RSD Ac.INH=15.86%). The method is also selective in cases of polytherapy as many drugs are associated (rifampicin, ethambutol, pyrazinamide, streptomycin). The matrix effect (plasma vs. water) is negligible for INH (3%), but statistically significant for Ac.INH (11%). The application of this validation design gave us the possibility to set up an easy and suitable method for INH therapeutic monitoring.

Separation methods for methotrexate, its structural analogues and metabolites

Methotrexate (MTX) is the prototype folate antagonist cytotoxic drug, employed in the therapy of solid tumors and leukaemias, and recently also as an immunosuppressive agent in organ transplantation, in the treatment of some autoimmune diseases and in the therapy of severe asthma. MTX is one of the very few antineoplastic drugs the therapeutic concentration monitoring of which is currently employed in clinical practice and can be routinely measured in biological samples by a number of different analytical techniques, among which are immunoenzymatic and chromatographic methods. Each technique has of course its own advantages in terms of sensitivity, specificity, speed, cost and level of expertise required. Along with therapeutic drug concentration monitoring and clinical pharmacology, fundamental research into the mechanism of action of antifolate drugs is still a field which requires the measurement of MTX, of its new analogues and of their metabolites in biological samples. This review summarizes the instrumental conditions and the performance of several published chromatographic methods employed to measure MTX, its metabolites and some analogues in clinical and biological research. More than 70 papers describing chromatographic assays for MTX and its metabolites have been published in the literature between 1975 and 2000. A wide array of experimental conditions for sample preparation, analyte separation and detection have been employed. According to their chemical properties, MTX, its metabolites and analogue drugs present in several biological samples (plasma, serum, saliva, urine, cerebrospinal fluid, tissue specimens) can be extracted, separated and detected under a variety of chromatographic conditions, i.e. on different stationary phases, under a wide choice of mobile phase conditions (acidic or neutral, employing ion-pair or micellar chromatography), followed by several detection techniques (UV-Vis spectrophotometry, pre- or post-column oxidation and fluorimetry, electrochemistry, mass spectrometry). Optimized methods allow simultaneous measurement within a few minutes of the plasma levels of MTX and its main metabolites at concentrations in the low-nM range. One special field which needs sensitive, fast and inexpensive methods for the detection and measurement of MTX is the monitoring of contamination in workplace environments, such as pharmaceutical industries and oncological hospital pharmacies, and in sewage waters. The measurement of the intracellular gamma-oligo-glutamate metabolites of biological folates, of MTX and of some analogue drugs is of great importance in basic pharmacological research. The existence of empirical quantitative relationships between the retention of individual oligomers under different chromatographic conditions and the number of added glutamic acid units allows identification of the metabolites even when authentic standards are not available.

Liquid chromatographic analysis and preliminary pharmacokinetics of methotrexate in cancer patients co-treated with docetaxel

A new HPLC method has been developed for the quantitative determination of methotrexate (MTX) and its 7-hydroxyl metabolite in human plasma. Samples were purified by protein precipitation with acetone and methanol, and a sample clean-up with a mixture of n-butanol and diethyl ether. The analytes were separated on an RP Inertsil ODS-80A column and eluted in a solvent system containing 5% (v/v) tetrahydrofuran in water (pH 2.0). UV absorption measurement was performed at 313 nm, and the detector response was linear in a concentration range of 10-10,000 ng/ml. The lower limit of quantitation of MTX was 10 ng/ml using 1 ml sample aliquots. Values for accuracy and (within-run and between-run) precision were between 95.5-111% and 3.69-11.0%, respectively, at four concentrations analyzed in quintuplicate on four separate occasions. The assay was applied to study the effects of docetaxel co-administration on the pharmacokinetics and metabolism of MTX in cancer patients.

Liquid-liquid extraction in the 96-well plate format with SRM LC/MS quantitative determination of methotrexate and its major metabolite in human plasma

A method involving the semirobotic liquid-liquid extraction (LLE) in deep-well 96-well plates was developed for the quantitation of the anti-cancer/antiinflammatory drug methotrexate (MTX) and its major metabolite, 7-hydroxymethotrexate (7OH-MTX) in human plasma. The extraction time for the sample preparation was relatively short with four 96-well plates (384 samples) prepared in approximately 90 min by one person. The sample extracts were each analyzed within 1.2 min using a positive ion turbo-ionspray selected reaction monitoring liquid chromatography/mass spectrometric (SRM LC/MS) method in which 768 samples were easily analyzed within 22 h (maximum of 820 samples in 24 h). Deuterated internal standards, MTX-d3 and 7OH-MTX-d3, were used. The calibration curves for MTX and 7OH-MTX were linear (R2 > 0.997) and ranged from 0.5 to 250 and 0.75 to 100 ng/mL, respectively. The limit of quantitation (LOQ) for MTX and 7OH-MTX was 0.5 and 0.75 ng/mL, respectively; persistent carryover from the autosampler limited the LOQ achievable. The limit of detection (LOD) was 0.05 ng/mL for MTX and 0.1 ng/mL for 7OH-MTX. The intra- and inter-assay precision and accuracy did not exceed 15% for both MTX and 7OH-MTX. The recoveries were 61% for MTX and 47% for 7OH-MTX. The method was validated and demonstrated to be robust with high precision and accuracy.

High-performance liquid chromatography of methotrexate for environmental monitoring of surface contamination in hospital departments and assessment of occupational exposure

In the frame of applicative research in occupational hygiene of hospital workplaces, we investigate hospital indoor contamination as a consequence of the use of antineoplastic drugs (ANDs), with the purpose of assessing exposure of medical and nursing personnel to potentially harmful doses of ANDs, and ultimately of yielding advice on safe operating procedures for manipulation of ANDs in hospitals and in house-care of cancer patients. Among the large number of currently employed ANDs, methotrexate (MTX) has been selected as a tracer of surface contamination, on the basis of its wide use in therapy, its ease of measurement and of its chemical properties relevant to persistence and transport in the indoor environment. MTX is a polyelectrolyte, with a high water, but lower organic solvent solubility, a negligible vapour pressure and a high chemical robustness to environmental stress, thus allowing to measure surface-to-surface carryover (e.g. from spillage or glove fingerprint) and indoor contamination due to aerosol transport (e.g. from syringe manipulation procedures). Monitoring of MTX in environmental samples such as swab washings of surfaces and objects requires an analytical method with characteristics of sensitivity, reproducibility, precision, analytical speed, ease of automation and robustness. We have therefore developed an analytical procedure which employs simple short-column RP-HPLC with UV detection, automated sample injection and a close analogue internal standard for improved precision and solid-phase extraction (SPE) for sample concentration. Our method has proven suitable for detecting traces of MTX on a wide variety of surfaces and objects, with a limit of quantification in the range of 50 microg/dm3 for direct injection of unconcentrated washings, corresponding to the possible detection of surface contamination as low as 1 microg/m3 and a limit of detection in the range of 10 ng/m2 for samples as large as 100 dm3 concentrated by SPE. We present preliminary results from a recent hospital case-study, assessing the contamination level of furniture and equipment in drug preparation areas. Spillage fractions as high as 5% of the employed mass (70-260 mg/day) are measured on the polythene-backed paper disposable hood cover sheet; traces of MTX in the microgram range can also be measured on floor surfaces, furniture and handles, even at a distance from the preparation hoods.

Therapeutic drug monitoring of antimetabolic cytotoxic drugs

Therapeutic drug monitoring is not routinely used for cytotoxic agents. There are several reasons, but one major drawback is the lack of established therapeutic concentration ranges. Combination chemotherapy makes the establishment of therapeutic ranges for individual drugs difficult, the concentration-effect relationship for a single drug may not be the same as that when the drug is used in a drug combination. Pharmacokinetic optimization protocols for many classes of cytotoxic compounds exist in specialized centres, and some of these protocols are now part of large multicentre trials. Nonetheless, methotrexate is the only agent which is routinely monitored in most treatment centres. An additional factor, especially in antimetabolite therapy, is the existence of pharmacogenetic enzymes which play a major role in drug metabolism. Monitoring of therapy could include assay of phenotypic enzyme activities or genotype in addition to, or instead of, the more traditional measurement of parent drug or drug metabolites. The cytotoxic activities of mercaptopurine and fluorouracil are regulated by thiopurine methyltransferase (TPMT) and dihydropyrimidine dehydrogenase (DPD), respectively. Lack of TPMT functional activity produces life-threatening mercaptopurine myelotoxicity. Very low DPD activity reduces fluorouracil breakdown producing severe cytotoxicity. These pharmacogenetic enzymes can influence the bioavailability, pharmacokinetics, toxicity and efficacy of their substrate drugs.

Separation of etoposide phosphate and methotrexate by capillary zone electrophoresis using UV detection with a high sensitivity cell

Etoposide phosphate and methotrexate are important anti-tumor chemotherapeutic agents. Our previously presented capillary zone electrophoresis (CZE) method using a high sensitivity cell (Z-cell) for quantitative analysis in biological media (urine, plasma) showed good precision and accuracy. The present results show that the investigation using a capillary with high sensitivity cell led to an approximately 10-fold improvement of the detection limit compared to standard capillaries. Plasma and urine samples were analyzed by using a calibration curve for drug concentrations between 0.1 and 100 microg/mL. Good detection limits and good relative standard deviations of the migration times and of the peak areas were observed in these experiments.

Application of a standardized coextractive cleanup procedure to routine high-performance liquid chromatography assays of teicoplanin and ganciclovir in plasma

Deproteinization of plasma samples with acetonitrile followed by coextracting acetonitrile and lipophilic solutes with chloroform, as already proposed for methotrexate, is stressed as a general sample cleanup procedure for liquid chromatography of highly polar drugs, and was validated for two more applications: teicoplanin and ganciclovir. A dedicated "prevalidation" experimental design was used to assess performances of both assays, including sample preparation. Deviations from linearity were less than 10% over the ranges of 3.1 to 50 mg/l (teicoplanin) and 0.2 to 15 mg/l (ganciclovir), respectively, and limits of quantitation were 0.09 and 0.01 mg/l, respectively. Mean chromatographic measurement R.S.D.s were 4.6% and 1.9%, respectively, with an additional mean cleanup R.S.D. of 2% for both. Mean analyte losses ascribable to cleanup were 6% and 2.5%, respectively from water, and 18% and 12%, respectively from the plasma matrix.