Combined thin-layer chromatography-photography-densitometry for the quantitation of cyclophosphamide and its four principal urinary metabolites

Paper Analytic Device to Detect the Presence of Four Chemotherapy Drugs

A paper analytic device, the chemoPAD, was developed and validated to visually detect methotrexate, doxorubicin, cisplatin, and oxaliplatin at concentrations commonly found in injectable dosage forms. By testing residual solution after patient treatment, the chemoPAD can be used to monitor drug quality without restriction of patient access to medication. The chemoPAD is produced by wax printing on Ahlstrom paper to create separate reaction areas and deposits small amounts of chemicals to create color changes in response to different active pharmaceutical ingredients (APIs). This creates a unique color bar code to identify each medication. Internal validation studies show that the chemoPAD has excellent sensitivity and specificity to differentiate between samples of 100% and 0% API, which is the distinction relevant to the majority of reported falsified chemotherapy cases. The platinum-containing drugs, cisplatin and oxaliplatin, can be detected semiquantitatively. The cards can be read either visually by comparison with a standard image or by using computer image analysis. Dosage forms were collected from the Ethiopian health care system and analyzed with the chemoPAD followed by high-performance liquid chromatography. A substandard sample was discovered and reported to the Ethiopian Food Medicine and Healthcare Administration and Control Authority.

Comparative metabolism of cyclophosphamide and ifosfamide in the mouse using UPLC-ESI-QTOFMS-based metabolomics

Ifosfamide (IF) and cyclophosphamide (CP) are common chemotherapeutic agents. Interestingly, while the two drugs are isomers, only IF treatment is known to cause nephrotoxicity and neurotoxicity. Therefore, it was anticipated that a comparison of IF and CP drug metabolites in the mouse would reveal reasons for this selective toxicity. Drug metabolites were profiled by ultra-performance liquid chromatography-linked electrospray ionization quadrupole time-of-flight mass spectrometry (UPLC-ESI-QTOFMS), and the results analyzed by multivariate data analysis. Of the total 23 drug metabolites identified by UPLC-ESI-QTOFMS for both IF and CP, five were found to be novel. Ifosfamide preferentially underwent N-dechloroethylation, the pathway yielding 2-chloroacetaldehyde, while cyclophosphamide preferentially underwent ring-opening, the pathway yielding acrolein (AC). Additionally, S-carboxymethylcysteine and thiodiglycolic acid, two downstream IF and CP metabolites, were produced similarly in both IF- and CP-treated mice. This may suggest that other metabolites, perhaps precursors of thiodiglycolic acid, may be responsible for IF encephalopathy and nephropathy.

Clinical pharmacokinetics of cyclophosphamide

Cyclophosphamide is an extensively used anticancer and immunosuppressive agent. It is a prodrug undergoing a complicated process of metabolic activation and inactivation. Technical difficulties in the accurate determination of the cyclophosphamide metabolites have long hampered the assessment of the clinical pharmacology of this drug. As these techniques are becoming increasingly available, adequate description of the pharmacokinetics of cyclophosphamide and its metabolites has become possible. There is incomplete understanding on the role of cyclophosphamide metabolites in the efficacy and toxicity of cyclophosphamide therapy. However, relationships between toxicity (cardiotoxicity, veno-occlusive disease) and exposure to cyclophosphamide and its metabolites have been established. Variations in the balance between metabolic activation and inactivation of cyclophosphamide owing to autoinduction, dose escalation, drug-drug interactions and individual differences have been reported, suggesting possibilities for optimisation of cyclophosphamide therapy. Knowledge of the pharmacokinetics of cyclophosphamide, and possibly monitoring the pharmacokinetics of cyclophosphamide in individuals, may be useful for improving its therapeutic index.

Separation methods for alkylating antineoplastic compounds

The separating method for alkylating neoplastic compounds were reviewed based on the classification of the Merck Index (12th Edition). Each section, whenever available or relevant, was subdivided according to the following approach: stability studies, extraction methods, gas chromatography, high-performance liquid chromatography and capillary electrophoresis. At the end of each chapter a separate table summarizing the main characteristics of the separating method were established. In particular LODs and/or LOQs were expressed as quantity to facilitate comparison between methods. This review highlights the problems to measure trace levels of these compounds into biological fluids with respect to their instability, adsorption to glass and plastic or derivatization requirements. Over the last decades, HPLC seems to be more popular than GC for separating the alkylating agents. The development of narrow- or microbore LC coupled to MS is certainly the way to further improve both separation and sensitivity obtained in the different papers surveyed for this review.

Cyclophosphamide and related anticancer drugs

This article presents an overview of the methods of bioanalysis of oxazaphosphorines, in particular, cyclophosphamide, ifosfamide, and trofosfamide as well as their metabolites. The metabolism of oxazaphosphorines is complex and leads to a large variety of metabolites and therefore the spectrum of methods used is relatively broad. The various methods used are shown in a table and the particularly important assays are described.

Simple and selective determination of the cyclophosphamide metabolite phosphoramide mustard in human plasma using high-performance liquid chromatography

A simple and selective assay for the determination of the alkylating cyclophosphamide metabolite phosphoramide mustard (PM) in plasma was developed and validated. PM was determined after derivatisation by high-performance liquid chromatography (HPLC) with ultraviolet detection at 276 nm. Sample pre-treatment consisted of derivatisation of PM with diethyldithiocarbamate (DDTC) at 70 degrees C for 10 min, followed by extraction with acetonitrile in the presence of 0.7 M sodium chloride. Phase separation occurred due to the high salt content of the aqueous phase. The HPLC system consisted of a C8 column with acetonitrile-0.025 M potassium phosphate buffer, pH 8.0, (32:68, v/v) as the mobile phase. The entire sample handling procedure, from collection at the clinical ward until analysis in the laboratory, was optimised and validated. Calibration curves were linear from 50 to 10,000 ng/ml. The lower limit of quantification and the limit of detection (using a signal-to-noise ratio of 3) were 50 and 40 ng/ml, respectively, using 500 microl of plasma. Within-day and between-day precisions were below 11% over the entire concentration range and the accuracies were between 100 and 106%. PM was found to be stable at -30 degrees C for at least 10 weeks both in plasma and as a DDTC-derivative in a dry sample. A pharmacokinetic pilot study in two patients receiving 1,000 mg/m2 CP in a 1-h infusion demonstrated the applicability of the assay.

Analysis of cyclophosphamide and five metabolites from human plasma using liquid chromatography-mass spectrometry and gas chromatography-nitrogen-phosphorus detection

An assay method for the quantification of cyclophosphamide (CY) and five metabolites from human plasma is presented. The procedure is adapted to the chemical properties of the compounds of interest: non-polar compounds are extracted into methylene chloride, concentrated and analyzed by GC-NPD after derivatization, and the remaining aqueous fraction is deproteinated with acetonitrile-methanol prior to separation via reversed-phase HPLC and detection using atmospheric pressure ionization (API)-MS. Standard curves are linear over the required range and reproducible over five months. Plasma concentration-time profiles of CY and metabolites from a patient receiving CY by intravenous infusion (60 mg/kg, once a day for two days) are presented.

Simultaneous determination of N,N',N"-triethylenethiophosphoramide, cyclophosphamide and some of their metabolites in plasma using capillary gas chromatography

A sensitive assay for the simultaneous determination of N,N',N"-triethylenethiophosphoramide (thioTEPA), its metabolite N,N',N"-triethylenephosphoramide (TEPA), cyclophosphamide (CP) and its metabolite 2-dechloroethylcyclophosphamide (2-DCE-CP) in plasma has been developed and validated. The analytes were determined using gas chromatography with nitrogen/phosphorus selective detection after liquid-liquid extraction with chloroform using 100 microl of plasma. Diphenylamine (for TEPA, thioTEPA and 2-DCE-CP) and imipramine (for CP) were used as internal standards. The limits of quantitation for thioTEPA, TEPA, CP and 2-DCE-CP were 5, 5, 50 and 250 ng/ml, respectively. Linear calibration curves were observed over two decades of concentration. Accuracy, within-day and between-day precision were less than 13% for all analytes. Stability of the analytes proved to be satisfactory for at least 1 month, stored at -70 degrees C. Analysis of samples obtained from patients receiving cyclophosphamide, thioTEPA and carboplatin in a high-dose regimen demonstrated the applicability of the assay.

Protection by transfected rat or human class 3 aldehyde dehydrogenase against the cytotoxic effects of oxazaphosphorine alkylating agents in hamster V79 cell lines. Demonstration of aldophosphamide metabolism by the human cytosolic class 3 isozyme

Expression of class 3 aldehyde dehydrogenase (ALDH-3) has been associated with acquired or inherent resistance to oxazaphosphorine (OAP) antineoplastic alkylating agents (eg. cyclophosphamide). We previously demonstrated that expression of transfected rat ALDH-3 can confer OAP-specific resistance in human MCF-7 cells (Bunting, K. D., Lindahl, R., and Townsend, A. J. (1994) J. Biol. Chem. 269, 23197-23203). However, the aldophosphamide intermediate inactivated by human class 1 ALDH (hALDH-1) has not proven to be a good substrate for the purified hALDH-3. We have examined the ability of transfected human or rat ALDH-3 to confer OAP resistance in V79/SDl cells. Clones expressing elevated human (386-5938 milliunits/mg) or rat (4-597 milliunits/mg, benzaldehyde/NADP+ substrate) ALDH-3 activity were 1.3- to 12-fold resistant to mafosfamide relative to control cells (<1 milliunit/mg). Resistance was correlated with hALDH-3 activity, and was reversed by pretreatment with the ALDH inhibitor diethylaminobenzaldehyde. Transfectants were cross-resistant to 4-hydroperoxycyclophosphamide and 4-hydroperoxyifosfamide but not to phosphoramide mustard, ifosfamide mustard, melphalan, or acrolein. DNA interstrand cross-links were reduced commensurately with the fold resistance to mafosfamide in the highest activity clone. A key finding was the detection of a metabolite, most likely carboxyphosphamide, that is formed only by cytosols from cells expressing either class 3 or class 1 ALDH.

Cyclophosphamide pharmacokinetics in children

1. Cyclophosphamide pharmacokinetics were measured in 38 children with cancer. 2. A high degree of inter-patient variation was seen in all pharmacokinetic parameters. Cyclophosphamide half-life varied between 1.1 and 16.8 h, clearance varied between 1.2 and 10.61 h-1 m-2 and volume of distribution varied between 0.26 and 1.48 1 kg-1. 3. The half-life of cyclophosphamide was prolonged at high dose levels (P = 0.008). 4. Children who had received prior treatment with dexamethasone showed a mean increase in clearance of 2.51 h-1 m-2 (P = 0.001) presumably as a result of CYP450 enzyme induction. 5. Treatment with allopurinol or chlorpromazine was associated with a significant increase in cyclophosphamide half-life (P < 0.001 in both cases). 6. Dose and concurrent treatment may influence cyclophosphamide metabolism in vivo and thus potentially alter the drugs therapeutic effect.

Colorimetric determination of cyclophosphamide and ifosphamide

A simple colorimetric method for the determination of cyclophosphamide and ifosphamide in pure and in dosage forms is suggested. It depends on the reaction of the secondary amino group in both, with nitrous acid, thus forming a nitroso derivative which can be measured at 325 nm for cyclophosphamide and 335 nm for ifosphamide. Beer's law is obeyed with concentrations from 20 to 90 micrograms ml-1 for cyclophosphamide and from 5 to 100 micrograms ml-1 for ifosphadmie, with repeatability of 99.83 +/- 0.256% and 99.72 +/- 0.649%, respectively. Application to different pharmaceutical preparations has shown no significant difference when compared with the B.P. 1988 method.

The determination of cyclophosphamide and its metabolites in blood plasma as stable trifluoroacetyl derivatives by electron capture chemical ionization gas chromatography/mass spectrometry

A method is described for the determination of the antitumour drug cyclophosphamide and six stable metabolites in plasma of cancer patients, namely dechloroethyl-cyclophosphamide, 4-keto-cyclophosphamide, carboxy-phosphamide, alcophosphamide, nor-nitrogen mustard and the N-chloroethyl-1,3-oxazolidine-2-one, as methyl and/or trifluoroacetyl derivatives by single ion monitoring gas chromatography/mass spectrometry, mostly in the electron capture chemical ionization mode. The isolation of most metabolites was performed by solid-phase C-18 extraction in weakly acidic medium. The phosphoramide mustard isolated under these conditions decomposes readily to the nor-nitrogen mustard during derivatization. The original nor-nitrogen mustard and the chloroethyl-1,3-oxazolidine-2-one were isolated by liquid extraction with ethyl acetate in alkaline medium. Recoveries of 75-99% were measured using spiked blank plasma samples. Quantitation of metabolites in patient plasma samples was performed using two sets of calibration curves for the concentration ranges of 1-100 ng and 0.1-10 micrograms of metabolite per millilitre of original plasma.

Preclinical pharmacokinetics and stability of isophosphoramide mustard

Stability and preclinical pharmacokinetics of isophosphoramide mustard (IPM), an active metabolite of ifosphamide, were investigated using analytical methods developed in this laboratory. For stability evaluation of IPM we used a rapid, high-pressure liquid chromatographic (HPLC) method by which IPM is analyzed directly from aqueous solutions without derivatization on a 10-microns C-18 reversed-phase column with theophylline as the internal standard. IPM in sodium phosphate buffers was found to undergo pH-dependent first-order degradations. At pH 7.4 and 38 degrees C, the IPM solution showed a half-life of 45 min. A gas chromatographic-mass spectrometry (GC/MS) method for the analysis of IPM in plasma was also developed. This method utilized solid-phase extraction with deuterium-labeled IPM as the internal standard. The routine detection limit for the assay was 50 ng/ml with within-run and between-run coefficients of variation of 6% and 11%, respectively. By this method, stability of IPM in plasma and in RPMI 1640 tissue culture medium was evaluated, and its pharmacokinetics in the Sprague-Dawley rat following i.v. administration at 40 mg/kg were investigated. IPM was found to be more stable in these media, with half-lives in the range of 100 min. IPM plasma pharmacokinetics were found to decline monoexponentially with terminal half-lives ranging from 6.8 to 18.7 min and total clearance between 6.0 and 18.3 ml/min. Plasma protein binding of IPM was found to be 55%, and the partition ratio between plasma and red blood cells of 4.9 to 1, respectively. Cytotoxicity of IPM to L1210 cells was evaluated, and the results indicated that the IC50 with 1-h and 4-h exposure was 33 and 15 microM, respectively. Based on these data, IPM plasma levels in the rat declined below the IC50 in about 1 h at this dose. More frequent dosing or infusion may be necessary to maintain adequate drug levels for antitumor activity when IPM is administered directly.

Combined thin-layer chromatography-photography-densitometry for the quantification of ifosfamide and its principal metabolites in urine, cerebrospinal fluid and plasma

A method has been devised for the determination of the anticancer drug ifosfamide and its principal metabolites in urine, plasma and cerebrospinal fluid (CSF). The urine and CSF samples are absorbed onto Amberlite XAD-2 eluting the compounds of interest with methanol. Plasma is deproteinated using cold acetonitrile and centrifuged to yield a clear supernatant. The eluate and supernatant are analyzed by thin-layer chromatography, with spot visualization using 4-(4-nitrobenzyl)pyridine. The plates are photographed for subsequent densitometeric analysis. The intra-assay coefficient of variation for each compound in both urine and plasma was less than 10% and the lower limit of detection was 1 microgram/ml. The method provides a means of determining the full spectrum of metabolic products of ifosfamide in patients and will allow detailed investigation of variability in metabolism and pharmacokinetics of this drug.

Pharmacokinetics and metabolism of cyclophosphamide in paediatric patients

The pharmacokinetics and metabolism of cyclophosphamide were studied in nine paediatric patients. Plasma samples were obtained from eight subjects and urine was collected from six children during a 24-h period after drug administration. Cyclophosphamide and its major metabolites phosphoramide mustard (PM), carboxyphosphamide (CX), dechloroethylcyclophosphamide (DCCP) and 4-ketocyclophosphamide (KETO) were determined in plasma and urine using high-performance thin-layer chromatography-photographic densitometry (HPTLC-PD). Cyclophosphamide (CP) was nearly, if not completely, cleared from plasma by 24 h after its administration. The plasma half-life of CP ranged from 2.15 to 8.15 h; it decreased following higher doses and was shorter than that previously reported for adult patients. Both the apparent volume of distribution (0.49 +/- 1.4 l/kg) and the total body clearance (2.14 +/- 1.4 l m-2 h-1) increased with increasing dose. Renal clearance ranged between 0.12 and 0.58 l/h (mean, 0.43 +/- 0.19 l/h). Between 5.4% and 86.1% of the total delivered dose was recovered as unchanged drug in the urine. The major metabolites identified in plasma and urine were PM and CX. One patient appeared to be deficient in CX formation. This study suggests that there is interpatient variability in the pharmacokinetics and metabolism of CP in paediatric patients. The shorter half-life and higher clearance as compared with adult values indicate faster CP metabolism in children.

Clinical pharmacokinetics of cyclophosphamide

Cyclophosphamide has been in clinical use for the treatment of malignant disease for over 30 years. It remains one of the most useful anticancer agents, and is also widely used for its immunosuppressive properties. Cyclophosphamide is inactive until it undergoes hepatic transformation to form 4-hydroxycyclophosphamide, which then breaks down to form the ultimate alkylating agent, phosphoramide mustard. Sensitive and specific methods are now available for the measurement of cyclophosphamide, its metabolites and its stereoisomers in plasma and urine. The pharmacokinetics of cyclophosphamide have been understood for many years; those of the cytotoxic metabolites have been described more recently. The pharmacokinetics are not significantly altered in the presence of hepatic or renal insufficiency. As activity resides exclusively in the metabolites, whose pharmacokinetics are not predicted by those of the parent compound, correlations between cyclophosphamide pharmacokinetics and pharmacodynamics have not been demonstrated. Cyclophosphamide is used in doses that range from 1.5 to 60 mg/kg/day. A steep dose-response curve exists, and reductions in dose can lead to unfavourable outcomes. Myelosuppression is the dose-limiting toxicity, although in the setting of bone marrow transplantation, escalation beyond that dosage range is limited by cardiac toxicity. Longer term complications of cyclophosphamide therapy include infertility and an increased incidence of second malignancies. Cellular sensitivity to cyclophosphamide is a function of cellular thiol concentration, metabolism by aldehyde dehydrogenases to form inactive metabolites, and the ability of DNA to repair alkylated nucleotides. Whether alteration of these cellular functions will lead to further improvements in clinical outcomes is an area of active investigation.

Chromatographic analysis of anticancer drugs

The present review on the methods for the analysis of anticancer drugs should be seen as an addition to the excellent work of Eksborg and Ehrsson published half a decade ago in this journal (Vol. 340, p.31). The style and format have been followed closely, with the focus again on chromatographic techniques. We felt it important to add a list of compound (group) structures as a service to the reader. Methods have been reviewed for alkylating agents, platinum compounds, antitumour antibiotics, antimetabolites, alkaloids, suramin, 1-hydroxy-3-amino-propylidene-1,1-bisphosphonate and tamoxifen.

The effect of route of administration and fractionation of dose on the metabolism of ifosfamide

The measurement of urinary ifosfamide, isophosphoramide mustard, dechloroethyl ifosfamide and carboxyifosfamide using high-performance thin-layer chromatography with photographic densitometry (TLC-PD) is described. This technique was also used to demonstrate the large inter-individual variation in the ifosfamide metabolic profile of patients receiving the drug as single-agent therapy for non-small-cell lung cancer. In addition, oral administration was shown to result in higher levels of these metabolites in the urine. Fractionation of the ifosfamide dose over several days resulted in increasing levels of metabolites in the urine, consistent with auto-induction of ifosfamide metabolism.