Determination of cytarabine and uracil arabinoside in human plasma and cerebrospinal fluid by high-performance liquid chromatography

Validation of a Novel Potentiometric Method Based on a Polymeric PVC Membrane Sensor Integrated with Tailored Receptors for the Antileukemia Drug Cytarabine

A simple, rapid and easy method is proposed for the detection of a cytostatic therapeutic drug, cytarabine, in real samples. The method is based on potentiometric transduction using prepared and characterized new ion-selective electrodes for cytarabine. The electrodes were integrated with novel man-tailored imprinted polymers and used as a sensory element for recognition. The electrodes revealed a remarkable potentiometric response for cytarabine over the linearity range 1.0 × 10⁻⁶–1.0 × 10⁻³ M at pH 2.8–4 with a detection limit of 5.5 × 10⁻⁷ M. The potentiometric response was near-Nernstian, with average slopes of 52.3 ± 1.2 mV/decade. The effect of lipophilic salts and plasticizer types on the potentiometric response was also examined. The electrodes exhibited an enhanced selectivity towards cytarabine over various foreign common ions. Validation and verification of the presented assay method are demonstrated by evaluating the method ruggedness and calculating the detection limit, range of linearity, accuracy (trueness), precision, repeatability (within-day) and reproducibility (between-days). The proposed ion-selective electrodes revealed good performance characteristics and possible application of these electrodes for cytarabine monitoring in different matrices. The electrodes are successfully applied to cytarabine determination in spiked biological fluid samples and in pharmaceutical formulations.

Simultaneous determination of cytosine arabinoside and its metabolite uracil arabinoside in human plasma by LC-MS/MS: Application to pharmacokinetics-pharmacogenetics pilot study in AML patients

Purine analogs like aracytine (AraC) are a mainstay for treating acute myeloid leukemia (AML). There are marked differences in drug dosing and scheduling depending on the protocols when treating AML patients with AraC. Large inter-patient pharmacokinetics variability has been reported, and genetic polymorphisms affecting cytidine deaminase (CDA), the liver enzyme responsible for the conversion of Ara-C to inactive uracil arabinoside (AraU) could be a culprit for either life-threatening toxicities or poor efficacy related to substantial changes in plasma exposure levels among patients. The quantitative determination of Ara-C in plasma is challenging due the required sensitivity because of the short half-life of this drug (i.e., <10 min) and the metabolic instability in biological matrix upon sampling possibly resulting in erratic values. We developed and validated a liquid chromatography tandem mass spectrometry method (UPLC-MS/MS) for the simultaneous determination of Ara-C and Ara-U metabolite in human plasma. After simple and rapid precipitation, analytes were successfully separated and quantitated over a 1-500 ng/ml range for Ara-C and 250-7500 ng/ml range for AraU. The performance and reliability of this method was tested as part of an investigational study in AML patients treated with low dose cytarabine and confirmed marked differences in drug exposure levels and metabolic ratio, depending on the CDA status of the patients. Overall, this new method meets the requirements of current bioanalytical guidelines and could be used to monitor drug levels in AML patients with respect to their CDA phenotypes.

Supercritical Fluid Chromatography and High-Performance Liquid Chromatography/Tandem Mass Spectrometric Methods for the Determination of Cytarabine in Mouse Plasma

The separation of cytarabine (ara-C) from the endogenous compounds in mouse plasma by packed-column supercritical fluid chromatography (pSFC) was achieved on bare silica stationary phase with an isocratic mobile phase composed of CO2/methanol solvent with addition of ammonium acetate. SFC is commonly assumed to be only applicable to nonpolar and relatively low-polarity compounds. In this work, a broader range of compound polarities amenable to pSFC with appropriate mobile-phase modifiers and additives under normal-phase retention mechanism was demonstrated. The pSFC was integrated with an atmospheric pressure chemical ionization source and a tandem mass spectrometer (MS/MS) to enhance the sensitivity, selectivity, and speed of the assay. The influence of mobile-phase components on chromatographic performance and ionization efficiency of the test compounds was investigated for improving the sensitivity and separation for the analyte and the internal standard. The pSFC-MS/MS approach requiring approximately 2.5 min/sample for the determination of ara-C at nanograms per milliliter in mouse plasma was partially validated with respect to stability, linearity, and reproducibility. The mouse plasma levels of ara-C obtained by the pSFC-MS/MS method were found to be consistent with those determined by various reversed-phase, high-performance liquid chromatography methods using a porous graphite carbon column, a mixed-mode column, or a C18 column in conjunction with an ion-pairing agent coupled to a tandem mass spectrometer.

Simultaneous separation and determination of Tarabine PFS and Adriblastine using micellar electrokinetic chromatography and high performance liquid chromatography. Application to some biological fluids

The simultaneous determination of Tarabine PFS and Adriblastine by two independent techniques, viz. micellar electrokinetic chromatography (MEKC) and high performance liquid chromatography (HPLC), has been studied. For MEKC analysis, separations and identifications were accomplished using uncoated fused-silica capillaries and injections were performed in the hydrodynamic mode. The running buffer consisted of 0.05 M borate/phosphate pH 8.70, with 0.10 M SDS at an operating voltage of 15.0 kV and the temperature held at 25.0 degrees C. Under these conditions, the migration times of Tarabine PFS and Adriblastine were 2.70 and 6.40 min, respectively. Calibration curves were established for 0.010-0.300 microg/mL (r = 0.99) Tarabine PFS and 8.000-120.0 microg/mL (r = 0.99) Adriblastine. The limit of detection (LOD) was estimated and found to be 0.003 and 3.000 microg/mL of Tarabine PFS and Adriblastine, respectively. The limit of quantitation (LOQ) was found to be 0.009 and 8.000 microg/mL of Tarabine PFS and Adriblastine, respectively. For HPLC analysis, separations and determinations were performed on teicoplanin stationary phase with reversed mobile phase containing methanol:buffer pH 4.05 (20.0:80.0%, v/v) at 285 nm. Calibration curves were established for 3.000-90.00 microg/mL (r = 0.99) Tarabine PFS and for 10.00-120.0 microg/mL (r = 0.99) Adriblastine. LOD and LOQ were estimated and found to be 0.950 and 2.050 microg/mL of Tarabine PFS and 3.130 and 9.250 microg/mL of Adriblastine, respectively. Both MEKC and HPLC methods were applied for the simultaneous determination of analytes in urine samples. It was found that 8.00-10.0% (Tarabine PFS) and 13.0-15.0% (Adriblastine) of the injected dose was recovered in urine samples with 99.5-102% recovery.

Osteryoung square wave stripping voltammetry at mercury film electrode for monitoring ultra trace levels of Tarabine PFS and its interaction with ssDNA

The electrochemical oxidation and reduction behaviour of adsorbed species of antimetabolic antineoplastic agent Tarabine PFS (Cytosar-U) in Sorensen buffer solution of different pH values at an in situ-mercury film electrode (MFE) is studied using cyclic voltammetry (CV) and Osteryoung square-wave stripping voltammetry (OSWSV). Optimal experimental and operational parameters have been selected for the drug preconcentration and determination in aqueous medium. Based on the adsorption and accumulation of Tarabine PFS using Osteryoung square-wave anodic stripping voltammetry (OSWASV) at MFE, the drug is easily detected as 0.134 ng/ml (5.51 x 10(-10) M). Calibration plots have been constructed at different accumulation times. The standard deviation (n=10) at a concentration level of 6 x 10(-8) M Tarabine PFS is 0.062. The interaction of ssDNA with the drug under the optimal conditions at pH 7.7 has been studied. The formal potentials E degrees and E degrees ' and the equilibrium constants K(1) and K(2) have been calculated for the free form of Tarabine PFS and the bonded form with ssDNA, respectively. It was found that K(2) value for the bonded oxidized form is 298 times than that of K(1) for the bonded reduced form. Therefore, ssDNA has been found to interact strongly with the oxidized form of the drug. The method has been used for the nanogram determination of ssDNA with 1.9% variation coefficient. Detection limit of 3 ng/ml ssDNA has been achieved. Possible interfering organic compounds, cations and anions have been tested. The method has been applied for the drug determination in urine samples, down to 0.23 ng/ml could be easily achieved in such samples.

Cytarabine release from comatrices of albumin microspheres in a poly(lactide–co-glycolide) film: in vitro and in vivo studies

Cytarabine (ara-C) was included in albumin microspheres and these microspheres were immersed in a poly(lactide-co-glycolide) (PLGA) film to constitute a comatrix system to develop a prolonged form of release. Cytarabine-loaded albumin microspheres were synthesized by emulsion, and 25 or 50 mg of drug were included in the disperse phase. Thus, microspheres with 46+/-4 microg drug/mg microspheres and 50+/-5 microg drug/mg microspheres were obtained, which means a percentage of incorporation efficiency of 42+/-4% and 25+/-2%, respectively. These cytarabine-loaded microspheres were used to prepare PLGA-comatrices. Kinetic release studies indicated that total cytarabine release only takes place in the presence of protease, probably due to the fact that glutaraldehyde establishes covalent links with the amine side group of the drug and cross-links it with the protein matrix. A slower kinetic release of the drug was obtained from PLGA-comatrices, although only 80% of the included cytarabine was released on day 7. The comatrices were subcutaneously implanted in the back of rats and in both cases the ara-C administered dose was 36 mg of ara-C per kg of body weight. The drug was detected in plasma 10 days. The mean residence time (MRT) of the drug administered by these comatrices was 87-91 times larger when compared to the value obtained when the drug was administered in solution by intraperitoneal injection. The histological studies show that a degradative process of the comatrices takes place. The comatrices do not damage surrounding tissue; a normal regeneration of the implanted zone was observed.

Chitosan microspheres in PLG films as devices for cytarabine release

Cytarabine was included in chitosan microspheres and several of these microspheres were embedded in a poly(lactide-co-glycolide) (PLG) film to constitute a comatrix system, to develop a prolonged release form. Chitosan microspheres, in the range of 92+/-65 microm, having good spherical geometry and a smooth surface incorporating cytarabine, were prepared. The cytarabine amount included in chitosan microspheres was 43.7 microg of ara-C per milligram microsphere. The incorporation efficiency of the cytarabine in microspheres was 70.6%. Total cytarabine release from microspheres in vitro was detected at 48 h. Inclusion of cytarabine-loaded microspheres in poly(lactide-co-glycolide) film initiated a slower release of the drug and, in this way, the maximum of cytarabine released (80%) took place in vitro at 94.5 h. Comatrices, with 8.7 mg of cytarabine, signifying a dose of 34.5 microg/kg, were subcutaneously implanted in the back of rats. Maximum plasma cytarabine concentration was 18.5+/-1.5 microg/ml, 48 h after the device implantation and the drug was detected in plasma for 13 days. The histological studies show a slow degradative process. After 6 months of implantation, most of the microspheres of the matrix seemed to be intact, the comatrix appeared surrounded by conjunctive tissue and small blood vessels and nerve packets were detected in the periphery of the implant.

Nonionic surfactant vesicles (niosomes) of cytarabine hydrochloride for effective treatment of leukemias: encapsulation, storage, and in vitro release

Niosome vesicles of cytarabine hydrochloride were prepared by a lipid hydration method that excluded dicetylphosphate. The sizes of the vesicles obtained ranged from 600 to 1000 nm, with the objective of producing more blood levels in vivo. The study of the release of drug from niosomes exhibited a prolonged release profile as studied over a period of 16 hr. The drug entrapment efficiency was about 80% with Tween 80, Span 60 and Tween 20; for Span 80, it was 67.5%. The physical stability profile of vesicular suspension was good as studied over a period of 4 weeks.

Pharmacokinetics of anticancer drugs in cerebrospinal fluid

OBJECTIVE

To examine the pharmacokinetics of anticancer drugs in the cerebrospinal fluid (CSF) during chemotherapy by the lumbar-ventricular (LV) and ventricular-lumbar (VL) routes.

CASE SUMMARY

A 69-year-old Japanese woman with disseminated glioblastoma received two LV and four VL courses of CSF perfusion chemotherapy with methotrexate, nimustine, and cytarabine hydrochloride. Samples of CSF from the ventricles and lumbar spinal canal were obtained via Ommaya reservoirs during one LV and one VL course. Drug concentrations in the CSF were measured by fluorescence polarization immunoassay or HPLC.

RESULTS

During LV CSF perfusion, the highest CSF drug concentrations in both the ventricles and the lumbar spinal canal were observed at the end of perfusion. During treatment, the concentrations of all three drugs in the lumbar spinal canal were higher than those in the ventricles. The CSF AUC of methotrexate in the ventricles was 16.1% of that in the lumbar spinal canal. During VL CSF perfusion, the highest drug concentrations were also observed at the end of perfusion. The drug concentrations in the lumbar spinal canal were initially lower than those in the ventricles. However, the concentrations of methotrexate and cytarabine in the lumbar spinal canal exceeded those in the ventricles 3 hours after perfusion. The AUC of methotrexate in the lumbar spinal canal was 174.9% of that in the ventricles.

CONCLUSIONS

The pharmacokinetics of anticancer drugs in ventricular CSF differ from those in lumbar CSF during LV and VL perfusion chemotherapy.

Poly(acrylamide-co-monoethyl itaconate) hydrogels as devices for cytarabine release in rats

This study has tested the application of three different copolymeric poly(acrylamide-co-monoethyl itaconate; A/MEI) hydrogels, 90A/10MEI, 75A/25MEI and 60A/40MEI, on the release of cytarabine (ara-C). The drug was incorporated in gels by placing it in the polymerization feed mixture and discs loaded with 5-50 mg ara-C were obtained. The amount of swelling at equilibrium in saline solution (NaCl, 0.9% w/w) was between 78 and 82% w/w, depending on the composition of the copolymer. The diffusion studies followed Fick's second law. The diffusion coefficients for swelling of the gels were between 9.30 x 10(-11) m2 s(-1) and 37.42 x 10(-11) m2 s(-1); those for release of ara-C were between 3.42 x 10(-11) m2 s(-1) and 10.25 x 10(-11) m2 s(-1). The activation energies for swelling were in the range 16.60 +/- 2.59-21.85 +/- 1.78 kJ mol(-1); those for ara-C release were 28.13 +/- 3.1-29.7 +/- 4.6 kJ mo(-1). To determine the applicability of these copolymers, 75A/25MEI gel was subcutaneously implanted in rats and the plasma concentration of the drug was determined by high-performance liquid chromatography. The concentration of ara-C in plasma (range 17.67 +/- 5.68-10.76 +/- 2.15 microg mL(-1)) was maintained during the first stages (2-8 h) and no drug was detected after 32 h. This route of administration was compared with intraperitoneal injection of the drug. In conclusion, ara-C can be incorporated in hydrogels and released in a pharmacologically active form. The concentration of ara-C in plasma is maintained for long enough to improve therapeutic results.

Evaluation of liquid chromatographic behavior of restricted-access media precolumns in the course of direct injection of large volumes of plasma samples in column-switching systems

The chromatographic behavior of an alkyl-diol silica (ADS, 25 x 4 mm I.D.) and a semipermeable surface (SPS, 10 x 10 mm I.D.) supports two types of restricted-access media (RAM), which served as precolumns in column-switching systems for direct injection of large volumes of plasma samples (500 microl), was studied with regard to peak performance, retention and column back pressure. The adsorption of matrix proteins both on sealings (porous frits and sieves) and packings was also examined. Columns of ADS and SPS were unchanged after the injection of 10-20 ml human plasma under normal working conditions. Even when changes occurred on the precolumns (>50 ml of plasma in total), it was still possible to regenerate the column performance by replacing the column sieves, or by washing and removing columns from the system for a period, since the changes were more related to the blockage of sealings and/or the adsorption of proteins on the hydrophilic surfaces. Proteins could eventually be unspecifically adsorbed on the hydrophobic ligand of the support. It was found on one ADS column that the retention decreased by 20% and the pressure increased 30 bar after an intensive loading of 75 ml plasma (injection volume, 500 microl) without reconditioning procedure. Studies showed that the column sealings played the most important role for the lifetime of RAM columns. For ADS columns, using sieves without polytetrafluoroethylene (PTFE) nets were the best. No significant difference in column life span between SPS and ADS was found.

Cytarabine trapping in poly(2-hydroxyethyl methacrylate) hydrogels: drug delivery studies

The release of cytarabine (ara-c) from poly(2-hydroxyethyl methacrylate) hydrogels cross-linked with different amounts of ethyleneglycol dimethacrylate (EGDMA) has been studied. The drug (range 5-25 mg) was trapped in polymer discs by including it in the feed mixture of polymerization. The drug delivery was followed by HPLC. The release was in accordance with Fickian behaviour. Total release of ara-C was reached after between 3 and 7 days depending on the percentage of EGDMA in the gels. A constant release rate of ara-C from the hydrogels was obtained, the time depending on the degree of cross-linking of the gels: 22 h for gels with 0.5% EGDMA, 32 h for gels with 5% EGDMA and 42 h for gels with 7% EGDMA; the amount of ara-C released being 50%, 80% and 85%, respectively, of the drug load of the gel discs. An increase of the release rate with the disc load was observed for each sort of hydrogel. Neither during the loading of the gels nor right through the drug release was degradation of ara-C observed.

Controlled release of cytarabine from poly(2-hydroxyethyl methacrylate-co-N-vinyl-2-pyrrolidone) hydrogels

Controlled release of cytarabine (ara-C) from poly(2-hydroxyethyl methacrylate-co-N-vinyl-2-pyrrolidone) [p(HEMA-co-VP)] hydrogels cross-linked with ethylene glycol dimethacrylate (EGDMA) is reported. Three compositions of copolymer, each one with a different cross-linking degree, have been studied: H50/VP50, H75/VP25, and H80/VP20. Ara-C (5-25 mg by disc) was trapped in the gels by including it in the polymerization feed mixture. The ara-C release time was between 1 day from H50/VP50/E0.5 discs and 16 days from H80/VP20/E15 discs. In all cases there is a time period for which the drug release rate is constant.

Alkylsulphonic acid ion pairing with radial compression columns for determining plasma or cerebrospinal fluid 1-beta-D-arabinofuranosylcytosine in pediatric pharmacokinetic analysis

In order to accurately and precisely measure plasma and cerebrospinal fluid (CSF) 1-beta-D-arabinofuranosylcytosine (Ara-C) in pediatric samples with adequate sensitivity and without interference, we have developed a reversed-phase ion-pairing technique utilizing the free amino group of the pyrimidine ring of Ara-C. Optimum resolution and separation was achieved utilizing a 4 microns C18 radial compression column. Ara-C and the internal standard 8-bromo-cyclic-AMP eluted at 6.5 and 4.6 min, respectively, with complete resolution. The minimum detectable amount is 2.5 pmol in a 50-microliters volume. The assay was linear in both plasma and CSF. Intra- and inter-day assay precision were less than 4% and 9%, respectively, for plasma with similar results obtained for CSF. Neither endogenous compounds nor commonly co-administered drugs interfere. Validity for our method was supported by the successful assay of over 400 pediatric plasma and 50 CSF samples for pharmacokinetic analysis. The method offers accuracy, precision, sensitivity and efficiency for plasma or CSF Ara-C determination.

Anticancer drug, ara-C, release from pHEMA hydrogels

This study investigates the controlled release of cytarabine (ara-C), an anticancer drug, from a polymeric matrix of lightly cross-linked poly(2-hydroxyethyl methacrylate) (pHEMA). The swelling of pHEMA discs in water was analysed as a function of temperature and thickness of xerogel discs. The fractional swelling was linear in (time)1/2 for short time periods. Drug release kinetics were examined as a function of temperature, initial drug load and thickness of pHEMA discs. The fraction of available drug release was also linear in (time)1/2 during the initial stages. These studies allow for the determination of diffusion coefficients for both the transport of water into the hydrogel and ara-C release from the polymer.

Chemotherapy with cytosine arabinoside in a child with Burkitt's lymphoma on maintenance hemodialysis and hemofiltration

A case of Burkitt's lymphoma (stage IV) in an 8-year-old boy with end-stage renal failure due to hemolytic uremic syndrome is reported. The boy was treated by maintenance hemodialysis (HD) and hemofiltration (HF). During chemotherapy treatment with continuous cytosine arabinoside (Ara-C) infusion (100 mg/m2/d) for 7 days, concentrations of Ara-C and its metabolite uracil arabinoside (Ara-U) were measured in blood, dialysate, and filtrate. Ara-C levels were always below 200 ng/ml and were only qualitatively detectable in blood, dialysate, and filtrate. Ara-U levels were higher than 200 ng/ml after 18 h treatment and were measured quantitatively. Ara-U clearance during 3 h HD was 92 ml/min and the calculated mass removal 14.7 mg/3 h. In contrast, the Ara-U clearance during 3 h HF was 14 ml/min and the mass removal was 6.7 mg/3 h. Ara-C and Ara-U are eliminated by HD and HF in anuric patients. A continuous infusion of 100 mg Ara-C m2/d during HD or HF treatment did not result in a serum concentration above 200 ng/ml.

Inhibition of fludarabine metabolism by arabinosylcytosine during therapy

The active 5'-triphosphate of arabinosyl-2-fluoroadenine (F-ara-ATP) increases the anabolism of arabinosylcytosine (ara-C), whereas ara-C 5'-triphosphate inhibits the phosphorylation of arabinosyl-2-fluoroadenine (F-ara-A) in human leukemia cells in vitro. These interactions have a potential impact on drug scheduling. Clinical trials of relapsed leukemia in which fludarabine (F-ara-A 5'-monophosphate) and ara-C were given in sequence provided the opportunity to evaluate the effects of ara-C infusion on two sequelae: the pharmacokinetics of F-ara-A in plasma and that of F-ara-ATP in leukemia cells. First, F-ara-A pharmacokinetics were altered by ara-C infusion. This was visualized as a transient increase in F-ara-A plasma levels during the ara-C infusion that was given 4 h after fludarabine. The perturbation in F-ara-A plasma levels was dependent on the dose ara-C. Second, peak F-ara-ATP concentrations were lower in leukemia cells of patients who received ara-C in addition to fludarabine as compared with those who received fludarabine alone. The terminal half-life of F-ara-A in plasma and the half-life of intracellular F-ara-ATP were reduced after the ara-C infusion in a concentration-dependent manner. Studies using purified deoxycytidine kinase support the conclusion that the increase in plasma levels of F-ara-A is in part the result of an effective competition by ara-C for phosphorylation by this enzyme, leading to a perturbation of the pharmacokinetics of intracellular F-ara-ATP.

Chromatographic methods for the bioanalysis of antiviral agents

The present review has concentrated on chromatographic techniques for the quantitative determination of antiviral drugs in biological samples. Special attention has been paid to the elements of chromatographic assays that are essential to ensure selectivity, sensitivity, accuracy and precision of the various methods. Wherever possible, attempts have been made to determine the suitability of the methods for application to investigations in pharmacokinetics in man and experimental animals, biopharmaceutics, therapeutic drug monitoring, metabolism and pharmacology. Because of the serious consequences of infection from material contaminated with viruses, special consideration has been given to the handling of contaminated samples. It was convenient to divide the antiviral drugs for the purpose of this review into two groups, the nucleoside and the non-nucleoside antiviral drugs. The nucleosides discussed are vidarabine, cytarabine, ribavirin, riboxamide, acyclovir, ganciclovir, desciclovir, carbovir, 2',3'-dideoxyadenosine, 2',3'-dideoxycytidine, zidovudine, 2',3'-dideoxyinosine, 2',3'-didehydro-3'-deoxythymidine, idoxuridine, 5-(2-bromovinyl)-2'-deoxyuridine, 2'-fluoro-5-iodoaracytidine and 5-iodo-2'-deoxycytidine. The non-nucleoside antiviral drugs discussed are arildone, amantidine, rimantidine, moroxydine, enviroxime, foscarnet and ampligen.

Extremely prolonged continuous intraperitoneal infusion of cytosine arabinoside

Intraperitoneal administration of ara-C produces a peritoneal/plasma concentration ratio of 330-1,000: In principle, optimal tumor-cell kill should be obtained when high ara-C concentrations ar maintained in the environment of the tumor for very long periods of time. A phase 1 study was undertaken to determine the maximum tolerated dose of ara-C that could be given as a continuous i.p. infusion for 3 weeks. A total of 14 patients with refractory malignancies were given 28 courses in the outpatient setting. Ara-C infusions were given using a portable programmable pump (Pancreatec Provider Model 2000). No significant side effects were observed in patients receiving 30 mg/m2 per day (five courses) or 40 mg/m2 per day x 21 days (seven courses). However, at a dose of 60 mg/m2 per day, although 10/16 courses were tolerated for at least 1 week, only 3/16 attempted courses could be continued for the full 3 weeks. The dose-limiting toxicity was chemical peritonitis, which occurred during 7/16 courses at this dose level and required termination of therapy in 4 courses. Myelosuppression was also observed at this dose. There was a large variation in the ara-C and ara-U peritoneal concentrations both within and between patients. The mean peritoneal ara-C concentration increased nonlinearly with ara-C dose whereas the mean ara-U concentration decreased. This study establishes the feasibility and safety of giving a cell-cycle-specific drug intraperitoneally over an extremely prolonged period. For subsequent studies a dose of 40 mg/m2 per day for 21 days is recommended.

Pharmacokinetics of cytosine arabinoside in cerebrospinal fluid and of its metabolite in leukemic cells

Concentrations of ara-CTP in leukemic cells isolated from CSF and of ara-C in lumbar CSF were measured following intraventricular ara-C administration in two girls with refractory meningeal leukemia. CSF samples were collected with a permanent intrathecal-lumbar catheter. In contrast to the comparatively short retention of ara-C in the CSF (t1/2 1.8 to 2.9 hours), there was a high accumulation and an extremely long retention of ara-CTP in the leukemic cells (t1/2 8.1 to 36 hours). The patients included in this study had an ara-C-resistant disease. No obvious relationship was seen between concentrations of ara-C in the CSF and of ara-CTP in the leukemic cells. Similar studies were performed after simultaneous intraventricular administration of hydrocortison and ara-C. Hydrocortison did not increase ara-CTP retention in the leukemic cells, nor did it effect CSF pleocytosis.

Stability of solutions of antineoplastic agents during preparation and storage for in vitro assays. III. Antimetabolites, tubulin-binding agents, platinum drugs, amsacrine, L-asparaginase, interferons, steroids and other miscellaneous antitumor agents

The stability of solutions of the antitumour antimetabolites, vinca alkaloids, podophyllotoxins, interferons, steroids and platinum drugs as well as maytansine, asparaginase, amsacrine, flavone-8-acetic acid, mitoguazone, and N-phosphonoacetyl-L-aspartate (PALA) is reviewed. Much of the published work has been done with biological, not stability-indicating, assays; thus, the relevant results should be used with caution. With this proviso, almost all of these drugs can be stored in solution for several days at room temperature or 4 degrees C. Most reports also suggest that the drugs that have been tested are stable when frozen in solution. For a number of the drugs, particular precautions are required; for instance, amsacrine should not be mixed with chloride-containing solutions, whereas cisplatin is most stable in solutions containing greater than 0.1 M chloride.

Exchange of cerebrospinal fluid in accidental intrathecal overdose of cytarabine

Intrathecal cytarabine (cytosine arabinoside) is included in many protocols for the treatment of acute lymphoblastic leukaemia of childhood. We report here the accidental administration of 200mg cytarabine intrathecally to a 4-year-old boy with CNS relapse. After the overdose the patient had dilated pupils during the first hour. One month later an unsteady gait and mild intention tremor in the hands were noted. By the exchange of cerebrospinal fluid with isotonic saline started 1 hour after overdose through a lumbar needle, about 27% of the administered dose was recovered. The estimated recovery in view of the time elapsed between overdose and start/end of the exchange procedure was 36%. This indicates that this procedure is of value in managing patients with heavy overdose of intrathecal cytarabine in hospitals without neurosurgical facilities.

Drug level monitoring: chromatography of some minor groups of drugs

Some important facts about the chromatographic separation of a number of selected categories of drugs are summarized. The data refer to the chromatographic method of choice, stationary phase, mobile phase (carrier gas), detection procedure and (where available) method sensitivity. Also, fundamental instrumental parameters, namely injector, column and detector temperature, carrier gas and mobile phase flow-rate and gradient set-up are reported here. In all cases also the source material used for analysis is specified. The data are presented in table form, each table dealing with a particular category of drugs. The following categories of drugs are being dealt with: anthelmintics, antiarteriosclerotics, antibacterials, anticholinergics and cholinergics, anticoagulants, antidiabetics, antiemetics, antimycotics, antihistamines, antimalarials, antiparasitics, antiparkinsonics, antitussives, antiulcer drugs, antiviral compounds, appetite depressants and immunosuppressives.

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.

Procedures for direct injections of untreated blood plasma into liquid chromatographic columns with emphasis on a pre-column venting technique

The stability of reversed-phase liquid chromatographic systems when untreated blood plasma samples are applied was studied with respect to retention, peak efficiency and column back-pressure. The influence of the content of organic solvents in the eluent, the flow-rate and the particle diameter of the support was investigated. Many of the column-deteriorating effects seem to be due to denaturation of the plasma proteins and the kinetics of this process. The stability is increased by decreasing the content of organic modifier in the eluent. The flow-rate should be moderate, as both high and low flow-rates give decreased stability. The stability increases with increasing particle size of the solid phase. A small pre-column is used (1) as a guard column and (2) to effect a pre-separation of the solute from plasma matrix components by a pre-column venting technique. The pre-column venting technique considerably increases the lifetime of the system and especially the separation column. Under optimal conditions hundreds of injections (10 microliters of plasma) can be performed without loss of stability.

High-performance liquid chromatographic assay for cytosine arabinoside, uracil arabinoside and some related nucleosides

A novel, dual-column high-performance liquid chromatographic method for determination of the anti-cancer drug cytosine arabinoside (Ara-C) and its major metabolite uracil arabinoside (Ara-U) has been developed. The analytical procedure is sensitive (25 ng/ml) and specific for Ara-C, Ara-U and the endogenous nucleosides that may influence response to Ara-C therapy, cytidine and deoxycytidine. Conventional and high dose calibration curves were linear and the method precise with the assay coefficient of variation for Ara-C and Ara-U not greater than 9.1% over the range of 0.1-10 micrograms/ml. Accuracy was determined to be within +/- 3 to 9% over this concentration range. Using this method, patient plasma samples from both conventional dose (100-200 mg/m2 per day) and high dose (3500-6500 mg/m2 per day) Ara-C can be simultaneously analyzed for Ara-C, Ara-U and nucleosides so that comparative pharmacokinetic and pharmacodynamic studies can be conducted.

Clinical results and pharmacokinetics of high-dose cytosine arabinoside (HD ARA-C)

Four patients with acute nonlymphoblastic leukemia and one malignant teratoma refractory to conventional chemotherapy were treated with high doses of cytosine arabinoside (HD ARA-C). They received up to 12 cycles of 1.8 to 3 g/m2 every 12 hours applied by 2-hour infusions. A total of 55 HD ARA-C infusions was performed. All leukemic patients responded. A complete clearance of blasts from the bone marrow was observed in two patients following 8-12 cycles of 3 g/m2. However, relapses occurred after three and seven weeks, in one case with resistance to HD ARA-C. The patient with malignant teratoma did not respond. No severe toxicity emerged even after repeated applications. Adverse reactions included moderate nausea and vomiting (4 patients), diarrhea (2 patients), hepatic dysfunction (1 patient), bone pain (1 patient), blurred vision (1 patient), conjunctivitis (1 patient), and exanthema with partial epidermiolysis (1 patient). Granulocytopenia occurring between 3-8 days after having started the therapy, subsided within 4-25 days. Plasma levels of ARA-C and the metabolite uracil arabinoside (ARA-U) were monitored. At steady state plasma concentrations of ARA-C were 32-97 microM (8-24 micrograms/ml). ARA-C disappeared from the plasma mono- or biphasic with a terminal half-life (t50%) of 7.8-12.6 minutes. The total clearance (Cl) of ARA-C varied between 1.7 and 2.9 liters/kg . h, and the distribution volume (Vss) between 0.44 and 0.86 liters/kg. Cerebrospinal fluid (CSF) levels of ARA-C reached 10-15% of steady state concentrations in plasma.