Rapid and simple method for the measurement of methotrexate and 7-hydroxymethotrexate in serum by high-performance liquid chromatography

High dose methotrexate chemotherapy: pharmacokinetics, folate and toxicity in osteosarcoma patients

AIMS

To investigate the relationships between pretreatment folate concentrations, MTX pharmacokinetics and acute toxicities following high dose methotrexate (HD MTX) therapy.

METHODS

MTX and its major extracellular metabolite 7-OH-MTX were measured in eight serum samples per HD MTX cycle in 65 consecutive osteosarcoma patients (288 cycles) and AUC (area under the blood concentration-time curve) was calculated. Pretreatment concentrations of folate in serum (S) and erythrocytes (ER) were determined. Hepatic, renal and haematological toxicities, assessed by routine laboratory parameters, as well as mucositis were graded according to National Cancer Institute Common Terminology Criteria for adverse events (CTCAE v.3.0). Dermatitis and pleuritis were reported as occurred or not.

RESULTS

S- and ER-folate pretreatment concentrations increased significantly with increasing number of HD MTX cycles (P < 0.001). ER-folate pretreatment concentrations were higher among males (median 610 nmol l⁻¹, 95% CI 550, 680) compared with females (median 465 nmol l⁻¹, 95% CI 430, 520, P < 0.001), but showed no correlation with MTX or 7-OH-MTX pharmacokinetics. We found correlations between alanine aminotransferase peak concentration (ALAT(max) ) and clearance of MTX (P < 0.001), gender (P < 0.001), age (P < 0.001) and 7-OH-MTX concentrations (P < 0.001), the latter being the main factor influencing ALAT(max) .

CONCLUSION

Our results suggest that 7-OH-MTX is involved in the development of HD MTX hepatic toxicity and that young female patients are most affected.

Methotrexate-added acrylic cement: biological and physical properties

BACKGROUND

Previous reports have demonstrated the suitability of adding different chemotherapeutic drugs to acrylic cement for the treatment of bone metastases. The best results so far have been obtained with methotrexate (MTX) for which diffusion from the implanted cement has been demonstrated both in vitro and in vivo. In this study the suitability of adding MTX to acrylic cement as local adjuvant chemotherapy was investigated.

METHODS

Using an in vitro model of human breast cancer cells we demonstrated that the drug is eluted in an active form able to exert a cytotoxic effect over a long period of time. The use of different concentrations of drug on the kinetic of elution and on the mechanical properties of cement was also evaluated.

RESULTS

The results obtained suggest that the release of MTX is higher at the beginning and progressively decreases over time being affected by the concentration of drug used. Our results also demonstrated that the addition and the subsequent elution of MTX does not alter the compressive properties of the cement.

CONCLUSION

These findings confirm the suitability of MTX-supplemented cement and support its use as an effective aid for the management of bone metastases requiring surgical curettage and acrylic cement implantation for structural support.

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.

In vitro stability study of methotrexate in blood and plasma samples for routine monitoring

A study was conducted to assess the stability of methotrexate (MTX) in pooled plasma and whole blood samples during an 11-day period. The concentrations were determined by liquid chromatography with UV detection over time, in the dark or in light, at different temperatures (4 degrees C or room temperature), and for a low and a high concentration level (0.6 and 2.5 microg/mL, 1.32 and 5.5 micromol/L, respectively). The accuracy, linearity, and variability of the method were assessed. This work demonstrates that blood samples are stable for 2 days at room temperature and for 6 days at 4 degrees C. Furthermore, there is no significant loss (<17%) in plasma at any of the investigated temperatures for at least 6 days. This study shows that whole blood samples can be stored for 3 days before centrifugation and that plasma samples can be reanalyzed after 6 days without any loss.

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.

Multi-targeted antifolate (MTA): pharmacokinetics of intraperitoneal administration in a rat model

AIMS

LY 231514 or MTA is a multi-targeted antifolate which has been used as an anticancer drug. It is an analogue of folic acid which has shown antitumour activity against various malignancies, particularly mesothelioma and colon cancer. For cancers with peritoneal surfaces extension, the advantage of intraperitoneal chemotherapy over intravenous chemotherapy administration is the high drug concentration that can be achieved locally. Using a rat model, this study was designed to compare the pharmacokinetics and tissue adsorption of intraperitoneal vs intravenous MTA.

METHODS

Sprague-Dawley rats were randomized into three groups according to dose and route of delivery of chemotherapy (10 mg/kg: intravenous; 10 mg/kg: intraperitoneal; 100 mg/kg: intraperitoneal). During the course of the experiment, peritoneal fluid and blood were sampled using a standardized protocol. At the end of the 3 hour procedure the rats were sacrificed, all urine was extracted and selected tissue samples were taken. One additional rat was studied over a 6 hour period for each group. The concentration of MTA in all samples was determined by high performance liquid chromatography (HPLC).

RESULTS

When MTA was delivered at 10 mg/kg the area under the curve (AUC) of the peritoneal fluid was significantly higher with intraperitoneal administration (10 778 microg/mlxmin) compared to intravenous administration (454 microg/mlxmin) (P<0.0001). This represents a 24-fold increase in exposure for tissues at peritoneal surfaces after intraperitoneal administration. The AUC ratio (AUC peritoneal fluid/AUC plasma) was 40.8 for intraperitoneal delivery as opposed to 0.014 for intravenous delivery (P=0.0063). The AUC ratio for intraperitoneal MTA at 100 mg/kg was 19.2. The half-life of MTA in the peritoneal fluid after intraperitoneal infusion was approximately 2 hours. There was a significant difference in MTA concentration in the mesenteric nodes and the abdominal wall (P=0. 0036 and 0.0017) and in the kidneys (P=0.0122) when intraperitoneal and intravenous administration were compared. Other tissue samples did not demonstrate any difference in drug concentration.

CONCLUSION

These experiments demonstrated that the exposure of peritoneal surfaces to MTA is significantly increased with intraperitoneal MTA administration. Due to the high likelihood of microscopic residual disease after resection of intra-abdominal malignancies, clinical studies to evaluate intraperitoneal MTA may be indicated.

Determination of methotrexate in human urine at trace levels by solid phase extraction and high-performance liquid chromatography/tandem mass spectrometry

For biological monitoring of hospital personnel occupationally exposed to antineoplastic agents, highly sensitive and specific methods are required. In order to detect trace MTX urinary concentrations, a precise and accurate high-performance liquid chromatography/tandem mass spectrometry (HPLC-MS/MS) procedure, incorporating solid phase extraction, has been developed. Urine samples were purified by solid phase extraction (SPE) on octadecyl bonded, endcapped silica SPE columns. After eluting with methanol, the solvent was evaporated obtaining a 25-fold concentration of the analyte. This procedure was validated by using 7-OHMTX as internal standard. Calibration curves had correlation coefficients always higher than 0.999, and the limit of detection was assessed at 0.2 microg L(-1). High specificity of the HPLC-MS/MS technique assures that no interfering substances are detected rather than the analyte of interest.

Determination of methotrexate in serum by high-performance liquid chromatography

A sensitive high-performance liquid chromatographic method with ultraviolet detection was developed to quantitate methotrexate in serum-based calibrators, controls and patient samples. Sample clean-up was achieved with C18 Sep-Pak Classic cartridges. The chromatographic separation was accomplished on a 5-microns Ultrasphere ODS Beckman column. 8-Chlorotheophylline was used as an internal standard. The method was validated by recovery, linearity, accuracy and precision studies. Two standard curves were constructed to cover the high and the low ends of the calibrator range (0.05-1.0 mumol/l). Response was found linear over the whole range of the calibrator set with a correlation coefficient of 0.999 and 1.00 for the low-level and the high-level curves, respectively. Accuracy varied from 12% at the lowest level to 1.2% at the highest level. The precision study showed a C.V. of 14.4% at the lowest level and 3.3% at the highest level.

Sensitive determination of methotrexate in monkey plasma by high-performance liquid chromatography using on-line solid-phase extraction

A high-performance liquid chromatographic method was developed for the sensitive determination of methotrexate (MTX) in monkey plasma using direct injection and on-line solid-phase extraction. After application of a 100-microliters aliquot of plasma to a pre-treatment column, the column was washed with 0.02 M phosphate buffer (pH 7) to eliminate plasma proteins and endogenous substances, and subsequently the adsorbed MTX was eluted. The MTX fraction was transferred to an analytical column by a column-switching (heart-cutting) technique, and MTX was analyzed using ion-pair chromatography with tetrabutylammonium bromide. More than 50 injections could be performed onto one pretreatment column. The accuracy, precision, reproducibility and linearity were satisfactory over a wide range of MTX concentrations (5-1000 ng/ml). The quantitation limit was 5 ng/ml with a signal-to-noise ratio of 5. The method was suitable for the pharmacokinetic study of MTX in monkey.

High-performance liquid chromatographic determination of methotrexate, 7-hydroxymethotrexate, 5-methyltetrahydrofolic acid and folinic acid in serum and cerebrospinal fluid

A method for the simultaneous determination of the antifolates methotrexate and 7-hydroxymethotrexate as well as the folates 5-methyltetrahydrofolic acid and folinic acid (5-formyltetrahydrofolic acid) in serum and cerebrospinal fluid (CSF) is described. High-performance liquid chromatography with gradient elution and dual detection (ultraviolet absorption and fluorescence) was used to separate and quantitate the analytes. Serum samples containing high levels of the substances of interest and CSF samples were injected directly onto the HPLC column. For determination of low concentrations, serum samples were subjected to a solid-phase extraction method for clean-up and concentration purposes. The determination limits were 10 ng/ml for both antifolates, 100 ng/ml for folinic acid, and 0.1 ng/ml for the physiologically occurring methylated folate which is about 1/100 the serum concentration in healthy children. The suitability of the method for pharmacokinetic monitoring of high-dose methotrexate therapy combined with leucovorin rescue administered to children with acute lymphoblastic leukemia was demonstrated. Minimum values of the serum folate during treatment ranged from 0.2 to 3.1 ng/ml. Even those very low concentrations could be reliably measured.

Determination of methotrexate in human urine at nanomolar levels by high-performance liquid chromatography with column switching

An high-performance liquid chromatographic method with column switching for the detection of less than 4 ng of methotrexate in the urine of oncologic nurses is described. Urine samples were purified by solid-phase extraction on silica-bonded phenyl columns, eluting impurities with ethyl acetate. After elution from the column, the analyte was concentrated ten-fold, evaporating the solvent. On a strong anion-exchange column (Nucleosil 100 SB), methotrexate was separated from the remaining interfering substances, was then switched to a reversed-phase column (LiChrospher 100 RP-18e), and finally eluted by a linear gradient in a solvent system consisting of ammonium formate buffer (pH 2.7) and acetonitrile. Absorbance was monitored at 310 nm. This method has proved to be suitable for detecting traces of methotrexate in urine in order to individualize risks and to reduce further the occupational safety hazard for hospital personnel.

2,4-diamino-7-hydroxy-pteridines, a new class of catabolites of methotrexate

Methotrexate remains a commonly used drug in the chemotherapy of various malignancies. The known catabolites are 7-hydroxy-methotrexate, formed in the liver, and diamino-methyl-pteroic acid formed in the gut. We report for the first time evidence that 2,4-diamino-7-hydroxy-pteridine derivatives are present in the biological fluids of patients on high-dose methotrexate protocols. So far, two major derivatives have been identified as 2,4-diamino-6-hydroxymethyl-7-hydroxy-pteridine and 2,4-diamino-6-methyl-7-hydroxy-pteridine. In regard to the actual knowledge of the catabolism of pteridines, these compounds are presumably formed by intestinal bacteria during enterohepatic circulation of the drug. Their slow clearance from the body raises the question of possible interference of these compounds on pteridine-dependent enzymes, which might explain in part some of the toxic effects of methotrexate.

7-Hydroxymethotrexate concentrations in serum and cerebrospinal fluid of children with acute lymphoblastic leukemia

Concentrations of methotrexate (MTX) and 7-hydroxymethotrexate (7-OH-MTX) were determined by HPLC in the serum and cerebrospinal fluid (CSF) of 29 children with acute lymphoblastic leukemia. CSF and serum samples were obtained at the end of 104 infusions of MTX given in a dose range of 0.5-8.0 g/m2. Concentrations, distribution ratios in serum and CSF for MTX and 7-OH-MTX, and the metabolic index were analyzed with regard to the MTX dose, age and clinical state of the patients. A wide inter-patient (2- to 12-fold) but narrower (1.1- to 3.5-fold) intra-patient variability of the concentrations was observed. A dose-proportional increase in the metabolite concentration was found in serum. On the other hand, the elevation of the level of metabolite in CSF was less than proportional to the dose. The CSF/serum distribution data suggest the existence of a saturable carrier system for MTX and 7-OH-MTX between serum and CSF that has lower affinity for 7-OH-MTX. No correlation was found between concentrations of MTX and 7-OH-MTX in the serum of patients receiving the same dose of MTX. No significant difference was observed in the values for metabolic index between relapsed patients and those who were in continuous complete remission. A significant correlation was found between age and metabolic index: the younger the patient, the higher the metabolite concentration measured in serum.

Comparative study on the pharmacokinetics of 7-hydroxy-methotrexate after administration of methotrexate in the dose range of 0.5-33.6 g/m2 to children with acute lymphoblastic leukemia

Concentrations of 7-hydroxy-methotrexate (7-OH-MTX) were determined in serum samples obtained after 266 infusions of methotrexate administered to 58 children with acute lymphoblastic leukemia. The dose of methotrexate (MTX) was in the range of 0.5-33.6 g/m2. Pharmacokinetic parameters (metabolic index, drug/metabolite ratio, half-life) of 7-OH-MTX and their relationship to the kinetics of methotrexate were analyzed. A great variability was observed in the extent and time-course of the metabolite formation. The concentration of the metabolite was higher than that of the parent compound at any examined time after the end of the 24 hours' infusion. The increase of 7-OH-MTX levels at the end of the methotrexate infusion was found to be proportionate to the increase of the dose of MTX. Males had significantly higher metabolite levels than did females (P less than 0.01) in the dose range of 0.5-8.0 g/m2. The age of the patients also significantly influenced the rate of the metabolite formation. The serial number of the treatment courses did not have effect on the metabolism of MTX. Dose dependency of the elimination half-life of the metabolite was found. Although a tendency was observed that patients in continuous complete remission had higher metabolite levels than those who relapsed, the difference was not significant. Further studies are needed to determine the clinical importance of 7-OH-MT.

Characterization of in-vitro drug release and biological activity of methotrexate-bovine serum albumin conjugates

Two series of methotrexate (MTX)-bovine serum albumin (BSA) conjugates have been prepared containing either 96 +/- 16 mg (mean +/- s.d.) or 32 +/- 13 mg of MTX per gram of conjugate. The conjugates released MTX in-vitro in a biphasic manner, the release rate being dependent on the quantity of MTX in the conjugate and on the pH of the release medium. An initial rapid release over 6 h appears to be due to physically adsorbed MTX with the slower secondary release due to covalently bound drug. The conjugates retain a degree of antineoplastic activity in-vitro, but this might be related to the small fraction of MTX that is tightly physically bound.

Determination of the antineoplastic agent methotrexate in body fluids by high-performance liquid chromatography with electrochemical detection

Some preliminary data concerning the anodic behaviour of the antineoplastic agent methotrexate are reported, and a high-performance liquid chromatographic method with electrochemical detection for its determination in human serum and urine is described. The method uses a reversed-phase C18 column and isocratic elution with amperometric detection on glassy carbon at +0.95 V vs. Ag/AgCl reference electrode. Sample treatment consists of a simple deproteinization step (serum) or an extraction procedure on Sep-Pak C18 cartridges (serum) or Amberlite column (urine). The detection limit for methotrexate in serum is 2.2 nmol/l. The method should prove useful for the evaluation of the drug pharmacokinetics in patients undergoing anticancer therapy.

Drug level monitoring: cytostatics

The present review on the quantification of cytostatic drugs has mainly been focussed on chromatographic techniques. Special attention has been paid to the precautions that have to be taken into account to ensure the selectivity and accuracy of the various methods. The various cytostatics that have been dealt with are: alkylating agents, antimetabolites, vinca alkaloids, antibiotics, cis-diamminedichloroplatinum, podophyllotoxine derivatives, and nitrosoureas.

Assay of methotrexate and 7-hydroxymethotrexate by gradient-elution high-performance liquid chromatography and its application in a high-dose pharmacokinetic study

A paired-ion high-performance liquid chromatographic method is described for the simultaneous determination of methotrexate (MTX) and its major metabolise, 7-hydroxymethotrexate (7-OH-MTX), in plasma and urine. In addition, this technique permits the separation of other known metabolites of MTX, such as DAMPA and MTX-polyglutamates. After selective extraction on an anion-exchange resin column, both compounds and the internal standard, aminopterin, were separated on a reversed-phase octadecylsilane column with UV-detection at 313 nm. The detection limits for plasma and urine samples were approximately 40 ng/ml (8.8 x 10(-8) M) for MTX and 100 ng/ml (2.1 x 10(-7) M) for 7-OH-MTX. This method was applied in pharmacokinetic studies following 24-h infusion of high-dose MTX in four patients during two successive treatments. After the end of the infusion, the mean apparent half-life for the metabolite was 19.1 h, while that for MTX was 8.8 h. A stepwise increase in the plasma concentrations of both MTX and its metabolite was observed during the second MTX infusion. This increase was reflected in the cumulative urinary excretion of both drug and its metabolite.

High-performance liquid chromatographic analysis of MTX, 7-OH-MTX and MTX derivatives: application to intracellular metabolism in tumor cells (HT 29)

In order to study the intracellular metabolism of Methotrexate (MTX) and the cytotoxicity of the antifolates, a specific paired-ion HPLC method has been developed which permits the simultaneous determination of DAMPA, MTX, 7-OH-MTX, MTX-G1, MTX-G2 and MTX-G3. Cells were incubated with 3H-MTX. The MTX metabolites were extracted, purified on SEP-PAK cartridges and further analysed by high-performance liquid chromatography (HPLC). The stationary phase was constituted by a C18 muBondapak and the mobile phase by 5 mM phosphate buffer (pH 7.4) containing 2.5 mM tetrabutylammonium nitrate. The elution was performed with a linear methanol gradient (20--30%). HPLC fractions were collected and radioactivity evaluated by beta counting (retention times: DAMPA = 12.93 min; MTX = 18.29 min; 7-OH-MTX = 21.13 min; MTX-G1 = 22.69 min; MTX-G2 = 26.81 min; MTX-G3 = 30.61 min). This analytical procedure was applied to separate and characterize multiple forms of MTX polyglutamate derivatives in HT 29, a human adenocarcinoma cell line varying the incubation time (4--18 h) and MTX concentration (0.6--10.6 micrometer). The incorporation process seems to be characteristic of a cell line resistant to MTX. The incorporation were very low and after a 4-h exposure time only 5% of the MTX was converted to polyglutamates. Between 1.6 and 10.6 microM MTX, no difference was observed in the polyglutamization. The defect in the incorporation of the drug and in the metabolization process in vitro could partially explain the failure of the MTX treatment in colorectal cancer.

An assay for methotrexate and its metabolites in serum and urine by ion-pair high-performance liquid chromatography

A high-performance liquid chromatographic assay for methotrexate and its metabolites, 7-hydroxy-methotrexate, 4-amino-4-deoxy-N10-methyl-pteroic acid and 7-hydroxy-4-amino-4-deoxy-N10-methyl-pteroic acid in the range 10 microg/l to 50 mg/l (2.2 x 10(-8) to 1.1. x 10(-4)M) has been developed using L-tryptophyl-L-glutamic acid as internal standard. Extraction was performed using an anion exchange resin (Dowex 1-X2) with subsequent ion-pair chromatography of the appropriate eluent fraction. The method has been found to be sensitive and precise for the analysis of both serum and urine, and may also be used for the quantitation of polyglutamyl metabolites.

High-performance liquid chromatographic assay of methotrexate, 7-hydroxymethortrexate, 4-deoxy-4-amino-N10-methylpteroic acid and sulfamethoxazole in serum, urine and cerebrospinal fluid

An automated high-performance liquid chromatographic system is described for separation and quantitation of the antineoplastic drug methotrexate and metabolites, and the antibiotic sulfamethoxazole in body fluids. The 40-min analysis utilizes a reversed-phase C18 column and gradient elution with detection by absorbance of ultraviolet light at 308 nm. The minimum detectable quantities with this assay are: methotrexate 4.4 ng (9.8 X 10(-12) mole); 4-deoxy-4-amino-N10-methylpteroic acid 11.9 ng (3.7 X 10(-11) mole); 7-hydroxymethotrexate 30 ng (6.5 X 10(-11) mole); sulfamethoxazole 125 ng (4.9 X 10(-10) mole). This analytical method should prove useful for therapeutic monitoring and pharmacokinetic studies of these compounds.