Simple high-performance liquid chromatographic method for the quantitation of 5-fluorouracil in human plasma

Antineoplastic drugs and their analysis: a state of the art review

We provide an overview of the analytical methods available for the quantification of antineoplastic drugs in pharmaceutical formulations, biological and environmental samples.

Attenuation effect of Abnormal Savda Munziq on liver and heart toxicity caused by chemotherapy in mice

Abnormal Savda Munziq (ASMq), an Uighur medicine formula commonly used in the treatment of cancer, has been speculated to possess antioxidative and antiproliferative effects, and to regulate immune activity. The present study was designed to systematically elucidate the toxicity-reducing activity of ASMq in mice undergoing combination chemotherapy with doxorubicin and 5-fluorouracil (5-FU). The mice were divided into normal (saline, 10 ml/kg) and doxorubicin + 5-FU groups (doxorubicin, 2.5 mg/kg; 5-FU, 10 mg/kg on alternate days). In addition, three groups received different doses of ASMq (2, 4 and 8 g/kg), in addition to doxorubicin (2.5 mg/kg) and 5-FU (10 mg/kg) treatment on alternate days. The histology of the heart and liver, superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) activity, malondialdehyde (MDA) concentrations in heart homogenate, and various biochemical parameters of the liver were evaluated. Compared with the normal control group, ASMq dose-dependently improved a number of variables, including body weight, liver index, transaminase and total protein, and partially normalized liver and cardiac pathology. ASMq restored activities of defense antioxidant enzymes SOD and GSH-Px towards normal levels, and decreased MDA concentration in dose-dependent manner. These results demonstrated that ASMq provides significant protection against doxorubicin + 5-FU combination induced hepatotoxicity and cardiotoxicity. Further studies are required to determine the effects of ASMq against doxorubicin + 5-FU-induced toxicity during chemotherapy in vivo.

Nitrosation and analysis of amino acid derivatives by isocratic HPLC

Amino acids are transformed by nitrosation with dinitrogen trioxide into their corresponding α-hydroxy acids, which are separated and analysed by HPLC, and used to quantify the original amino acid concentration in samples.

Evaluation of a closed-system cytotoxic transfer device in a pharmaceutical isolator

PURPOSE

The occupational risk associated with handling of cytotoxic anticancer drugs is well documented and, in many countries, pharmaceutical isolators are used to contain cytotoxic residues during preparation of cytotoxic infusions. Isolators are difficult to clean leading to concerns that cytotoxic contamination from the work area could be transferred to surfaces of products leaving the isolator. This study investigated the surface contamination arising from the preparation of five anticancer drug infusions (Epirubicin, Fluorouracil, Cisplatin, Oxaliplatin and Carboplatin) in a pharmaceutical isolator and compared use of a conventional syringe and needle technique with a closed-system drug transfer device (CSDTD).

METHODS

Wipe samples were taken over 1 week from pre-defined areas in the isolator, gloves, preparation mats, and also from the surfaces of prepared cytotoxic infusion bags and pre-filled syringes to obtain baseline surface contamination data. Following operator familiarisation, the CSDTD was then introduced and sampling repeated for a further week (intervention period). The samples obtained were analysed using validated HPLC-UV, HPLC-FL and ICP-MS techniques, as appropriate.

RESULTS

All surfaces sampled during baseline, including external surfaces of infusions and syringes, were contaminated with each marker drug. During the intervention phase, isolator surfaces were free from detectable contamination and the contamination measured on gloves, preparation mats and surface of infusions was markedly reduced. The frequency of contamination on syringe and infusion surfaces was also lower.

CONCLUSION

Surface contamination from cytotoxic infusion preparation in a pharmaceutical isolator was significant and could transmit cytotoxic residues to patient and public areas via infusion surfaces. The frequency and amount of contamination were reduced by the CSDTD.

Bioanalytical method validation: An updated review

The development of sound bioanalytical method(s) is of paramount importance during the process of drug discovery and development, culminating in a marketing approval. The objective of this paper is to review the sample preparation of drug in biological matrix and to provide practical approaches for determining selectivity, specificity, limit of detection, lower limit of quantitation, linearity, range, accuracy, precision, recovery, stability, ruggedness, and robustness of liquid chromatographic methods to support pharmacokinetic (PK), toxicokinetic, bioavailability, and bioequivalence studies. Bioanalysis, employed for the quantitative determination of drugs and their metabolites in biological fluids, plays a significant role in the evaluation and interpretation of bioequivalence, PK, and toxicokinetic studies. Selective and sensitive analytical methods for quantitative evaluation of drugs and their metabolites are critical for the successful conduct of pre-clinical and/or biopharmaceutics and clinical pharmacology studies.

RGD modified albumin nanospheres for tumour vasculature targeting

Objectives

Cyclic arginine-glycine-aspartic acid (RGD) peptide-anchored sterically stabilized albumin nanospheres (RGD-SN) have been investigated for the selective and preferential presentation of carrier contents at angiogenic endothelial cells overexpressing avb3 integrins on and around tumour tissue. Their targetabilty was assessed.

Methods

Albumin nanospheres were formulated, conjugated with RGD/RAD peptide and characterized on the basis of size and size distribution. The control Arginine-Alanine-Aspartic acid (RAD) peptide-anchored sterically stabilized nanospheres (RAD-SN) and nanosphere with 5 mol% PEG (SN) without peptide conjugate were used for comparison with RGD-SN for in vitro cell binding, in vivo organ distribution and tumor angiogenesis studies.

Key findings

The average size of all nanospheres prepared was approximately 100 nm and maximum drug entrapment was 67.2 ± 5.2%. In-vitro endothelial cell binding of nanospheres exhibited 8-fold higher binding of RGD-SN to human umbilical vein endothelial cells in comparison with the SN and RAD-SN. RGD peptide-anchored nanospheres were significantly (P ≤ 0.01) effective in the prevention of lung metastasis, angiogenesis and in effective regression of tumours compared with free fluorouracil, SN and RAD-SN. Results indicated that cyclic RGD peptide-anchored sterically stabilized nanospheres bearing fluorouracil were significantly (P ≤ 0.01) active against primary tumour and metastasis than the nontargeted sterically stabilized nanospheres and free drug.

Conclusions

Cyclic RGD peptide-anchored sterically stabilized nanospheres appears promising for targeted cancer chemotherapeutics.

Polymeric nanospheres modified with YIGSR peptide for tumor targeting

YIGSR peptide anchored pegylated nanospheres (YIGSR-SN) loaded with 5-fluorouracil (5-FU) were investigated for selective and preferential presentation of carrier contents at angiogenic endothelial cells over-expressing laminin receptors on and around tumor tissue and thus for assessing their targetability. Pegylated nanosphere (SN) without peptide conjugate were used for comparison. The average size of all nanosphere preparations prepared was approximately 108 nm and maximum drug entrapment was 68.5 +/- 5.2%. In vitro endothelial cell binding of nanospheres exhibited 8-fold higher binding of YIGSR-SN to HUVEC in comparison to the SN. Spontaneous lung metastasis and angiogenesis assays show that YIGSR peptide anchored nanospheres are significantly (p <or= 0.05) effective in the prevention of lung metastasis and angiogenesis compared to free 5-FU and SN. In therapeutic experiments, 5-FU, SN, and YIGSR-SN were administered intravenously on day 4 at the dose of 10 mg 5-FU/kg body weight to B16F10 tumor bearing BALB/c mice resulting in effective regression of tumors in YIGSR-SN compared with free 5-FU and SN. Results indicate that YIGSR peptide anchored pegylated nanospheres bearing 5-FU are significantly (p <or= 0.05) active against primary tumor and metastasis than the non-targeted pegylated nanospheres and free drug. Thus, YIGSR peptide anchored pegylated nanospheres hold potential of targeted cancer chemotherapeutics.

Liposomes modified with YIGSR peptide for tumor targeting

YIGSR peptide anchored sterically stabilized liposomes (YIGSR-SL) were investigated for selective and preferential presentation of carrier contents at angiogenic endothelial cells overexpressing laminin receptors on and around tumor tissue and thus for assessing their targetabilty. In vitro endothelial cell binding of liposomes exhibited 7-fold higher binding of YIGSR-SL to HUVEC in comparison to the nontargeted sterically stabilized liposomes (SL). Spontaneous lung metastasis and angiogenesis assays show that YIGSR peptide anchored liposomes are significantly (P <or= 0.01) effective in the prevention of lung metastasis and angiogenesis compared to free 5-fluorouracil (5-FU) and SL. YIGSR-SL was very effective in regression of tumors in BALB/c mice bearing B16F10 melanoma cells. Results indicate that YIGSR peptide anchored sterically stabilized liposomes bearing 5-FU are significantly (P <or= 0.01) active against primary tumor and metastasis than the SL and free drug. Thus, YIGSR peptide anchored sterically stabilized liposomes hold potential of targeted cancer chemotherapeutics.

A review of analytical methods for the determination of 5-fluorouracil in biological matrices

5-Fluorouracil (5-FU) is a cytostatic agent that has been widely used in the treatment of various solid tumours for more than 20 years, and is still considered to be among the most active antineoplastic agents in advanced colorectal cancer and malignancies of the head and neck. A large number of non-chromatographic and chromatographic methods for the quantitation of 5-FU, related prodrugs and their metabolites in biological matrices have been developed in the last 30 years to support preclinical and clinical studies. However, 5-FU monitoring has not been widely used, at least not in the USA, and certainly not outside the clinical research setting, given the absence of simple, fast and inexpensive testing methods for 5-FU monitoring. Recent developments with testing based on liquid chromatography-tandem mass spectrometry and a nanoparticle antibody-based immunoassay may facilitate routine monitoring of 5-FU in daily clinical practice. In this review the advantages and disadvantages of the bioanalytical methods developed and used for 5-FU, its metabolites and related prodrugs are discussed.

Development and characterization of 5-FU bearing ferritin appended solid lipid nanoparticles for tumour targeting

Ferritin coupled solid lipid nanoparticles were investigated for tumour targeting. Solid lipid nanoparticles were prepared using HSPC, cholesterol, DSPE and triolien. The SLNs without ferritin which has similar lipid composition were used for comparison. SLNs preparations were characterized for shape, size and percentage entrapment. The average size of SLNs was found to be in the range 110-152 nm and maximum drug entrapment was found to be 34.6-39.1%. In vitro drug release from the formulations is obeying fickian release kinetics. Cellular uptake and IC50 values of the formulation were determined in vitro in MDA-MB-468 breast cancer cells. In vitro cell binding of Fr-SLN exhibits 7.7-folds higher binding to MDA-MB-468 breast cancer cells in comparison to plain SLNs. Ex-vivo cytotoxicity assay on targeted nanoparticles gave IC50 of 1.28 microM and non-targeted nanoparticles gave IC50 of 3.56 microM. In therapeutic experiments, 5-FU, SLNs and Fr-SLNs were administered at the dose of 10 mg 5-FU/kg body weight to MDA-MB-468 tumour bearing Balb/c mice. Administration of Fr-SLNs formulation results in effective reduction in tumour growth as compared with free 5-FU and plain SLNs. The result demonstrates that this delivery system possessed an enhanced anti-tumour activity. The results warrant further evaluation of this delivery system.

Liposomes Modified with Cyclic RGD Peptide for Tumor Targeting

Cyclic RGD peptide anchored sterically stabilized liposomes (RGD-SL) were investigated for selective and preferential presentation of carrier contents at angiogenic endothelial cells overexpressing alphavbeta3 integrins on and around tumor tissue and thus for assessing their targetabilty. Liposomes were prepared using distearoylphosphatidylcholine (DSPC), cholesterol and distearoylphosphatidylethanolamine-polyethyleneglycol-RGD peptide conjugate (DSPE-PEG-RGD) in a molar ratio 56:39:5. The control RAD peptide anchored sterically stabilized liposomes (RAD-SL) and liposome with 5 mol% PEG (SL) without peptide conjugate which had similar lipid composition were used for comparison. The average size of all liposome preparations prepared was approximately 105 nm and maximum drug entrapment was 10.5+/- 1.1%. In vitro endothelial cell binding of liposomes exhibited 7-fold higher binding of RGD-SL to HUVEC in comparison to the SL and RAD-SL. Spontaneous lung metastasis and angiogenesis assays show that RGD peptide anchored liposomes are significantly (p<0.01) effective in the prevention of lung metastasis and angiogenesis compared to free 5-FU, SL and RAD-SL. In therapeutic experiments, 5-FU, SL, RGD-SL and RAD-SL were administered intravenously on day 4 at the dose of 10 mg 5-FU/kg body weight to B16F10 tumor bearing BALB/c mice resulting in effective regression of tumors compared with free 5-FU, SL and RAD-SL. Results indicate that cyclic RGD peptide anchored sterically stabilized liposomes bearing 5-FU are significantly (p<0.01) active against primary tumor and metastasis than the non-targeted sterically stabilized liposomes and free drug. Thus cyclic RGD peptide anchored sterically stabilized liposomes hold potential of targeted cancer chemotherapeutics.

Quantitation of 5-fluorouracil (5-FU) in human plasma by liquid chromatography/electrospray ionization tandem mass spectrometry

5-Fluorouracil (5-FU) has long had a place in the treatment of many malignancies. 5-FU plasma concentrations have been correlated with toxicity and efficacy, and therapeutic drug monitoring has been reported to result in an improved response/toxicity balance. We report validation, according to FDA guidelines, of a hydrophilic interaction chromatography (HILIC) liquid chromatography/tandem mass spectrometry (LC/MS/MS) assay for the sensitive, accurate and precise quantitation of 5-FU in human plasma. The assay employed an isotopically labeled 5-FU internal standard and ethyl acetate extraction. Separation was achieved with an amino column and an isocratic mobile phase of 0.1% formic acid in acetonitrile/water (97:3, v/v), followed by a wash. Detection consisted of electrospray, negative-mode ionization tandem mass spectrometry in the multiple reaction monitoring (MRM) mode. The accuracy was 96.0-102.2%, and precision was 2.1-7.5% in the concentration range of 10-10 000 ng/mL. Recovery from plasma was 46.0-72.6%, and ion suppression was 9.8-25.7%. Plasma freeze/thaw stability was 87.5-104.3%, and stability for 4 h at room temperature was 98.7-100.0%. This assay is currently being used to quantitate 5-FU in human plasma samples.

Design and development of folate appended liposomes for enhanced delivery of 5-FU to tumor cells

Folate appended sterically-stabilized liposomes (FA-SL) were investigated for tumor targeting. Liposomes were prepared using HSPC, cholesterol and FA-polyethylene glycol (PEG)-SA. The liposomes with polyethylene glycol (PEG) without folic acid which has similar lipid composition were used for comparison. Liposomal preparations were characterized for shape, size and percent entrapment. The average size of liposomes was found to be in range 124-163 nm and maximum drug entrapment was found to be 34.2-40.3%. In vitro drug release from the formulations is obeying fickian release kinetics. Cellular uptake and IC(50) values of the FR-targeted formulation were determined in vitro in FR (+) B16F10 melanoma cells. In vitro cell binding of FA-SL exhibits 11-folds higher binding to B16F10 melanoma cells in comparison to SL. In vivo cytotoxicy assay on FR targeted liposomes gave IC(50) of 1.87 microM and non-targeted liposomes gave IC(50) of 4.02 microM. In therapeutic experiments 5-fluorouracil (5-FU), SL and FA-SL were administered at the dose of 10 mg 5-FU/kg body weight to B16F10 tumor bearing Balb/c mice. Administration of FA-SL formulation results in effective reduction in tumor growth as compared with free 5-FU and SL. Results indicate that folic acid appended SL bearing 5-FU are significantly (P < 0.01) active against primary tumor and metastasis than non-targeted sterically-SL. Thus, it could be concluded that folate coupled liposomal formulations enhanced drug uptake by tumor cells.

Hydrophilic interaction liquid chromatography–APCI–mass spectrometry determination of 5-fluorouracil in plasma and tissues

A simple and fast analytical method using hydrophilic interaction liquid chromatography (HILIC) coupled with mass spectrometry was developed to analyse 5-fluorouracil (5-FU) in plasma and tissues. The HILIC system overcomes problems reported in obtaining satisfactory retention of 5-FU with other types of HPLC systems. After addition of internal standard (IS) (5-Chlorouracil (5-CU)), plasma proteins were precipitated with acetonitrile, and tissue samples homogenised with a micro-dismembrator. The analysis was performed using a polymer-based column (Ashaipak NH2) and the compounds were eluted under gradient conditions at 1 ml/min using a mobile phase containing a mixture of ammonium formate and acetonitrile. MS detection used a API 4000 mass spectrometry with heated nebulizer source and multiple reaction monitoring operated in the negative ion mode. The mass transitions of 5-FU and its internal standard were 129 m/z-->42m/z and 145 m/z-->42 m/z, respectively. The lower limits of quantitation in plasma and tissues were about 5 ng/ml and 10 ng/g, respectively, using 25 microl of plasma and 50mg of tissue. Good linearity, accuracy and precision were obtained in all matrices tested. The suitability and robustness of the method for in vivo samples were confirmed by analysis of mouse plasma, muscle and tumour from animals dosed with 5-FU.

Validated liquid chromatographic determination of 5-fluorouracil in human plasma

A sensitive, reproducible, selective and accurate high performance liquid chromatographic (HPLC) method for the quantitative determination of 5-flurorouracil in plasma has been developed and validated using isocratic elution and UV detection. The method provides a selective quantifications of 5-flurorouracil without any interference of the endogenous uracil. The assay is performed after a double extraction of 5-flurorouracil and thymine (internal standard) from human plasma using ethyl acetate. The drug and the internal standard were eluted from a Genesis C(18) analytical column at ambient temperature with mobile phase consisting of methanol:water (10:90, v/v) adjusted to pH 3.2 with perchloric acid at a flow rate of 1.0 ml/min. The effluent was monitored with an ultraviolet detector at 260 nm. Quantification was achieved by the measurement of the peak-height ratios and the limit of quantification for 5-flurorouracil in plasma was 30 ng/ml. The retention times for 5-flurorouracil, uracil, and thymine were 4.5, 6.0, and 9.0, respectively. The intra-day coefficient of variation (CV) ranged from 1.35 to 4.53% at three different concentrations and the inter-day CVs varied from 1.29 to 4.98%. The relative and absolute recoveries varied from 96 to 101%. Stability tests showed that 5-flurorouracil is stable for at least 72 h in plasma after freezing. The simple method may permit the assessment of 5-flurorouracil plasma concentrations for pharmacokinetic studies in combination with clinical trials.

Simple determination of capecitabine and its metabolites by liquid chromatography with ultraviolet detection in a single injection

Capecitabine (N4-pentoxycarbonyl-5'-deoxy-5-fluorocytidine, Xeloda), a prodrug of 5-fluorouracil (5-FU), is an oral tumor-selective fluoropyrimidine carbamate approved in the treatment of colorectal and breast cancer. It has a preferential activation to 5-FU by thymidine phosphorilase (TP) in target tumor tissues through a series of three metabolic steps minimizing the exposure of normal tissues to 5-FU. It offers the potential of less gastrointestinal toxicity and advantages in terms of convenience and quality of life for the patient, in addition to cost-effectiveness as compared with intravenous 5-FU chemotherapy. We developed a high performance liquid chromatography assay for the determination of plasma capecitabine and its nucleoside metabolite concentrations and 5-FU catabolite dihydro-5-fluorouracil in a single step extraction and a single HPLC injection. The retention times of dihydro-5-fluorouracil, 5-FU, 5'-deoxy-5-fluorouridine (5'-DFUR) and capecitabine were 3.6, 4.4, 11.4 and 20.4 min, respectively and the internal standard retention times were 8.7 and 12.2 min for 5-bromouracil (5-BU) and tegafur, respectively. The limit of detection was 0.01 microg/ml for capecitabine and its nucleoside metabolites and the limit of quantification was 0.025 microg/ml. Extraction efficiency was >80% with a single solvent mixture extraction step for all analytes of interest. The assay had good precision, the within-day and between-day standard deviation of the mean (R.S.D.) being <10% in the linear range 0.025-10 microg/ml. The authors conclude that the method described here is ideally suited for the therapeutic monitoring of capecitabine and its metabolites.

Determination of 5-fluorouracil and its prodrug tegafur in plasma and tissue by high-performance liquid chromatography in a single injection: validation for application in clinical pharmacokinetic studies

Tegafur, a prodrug of 5-fluorouracil (5-FU), is an oral fluorouracil antitumor drug used for the management of adenocarcinomas. It has an efficacy similar to that of intravenous 5-FU, with potential advantages in terms of convenience and quality of life for the patient and cost-effectiveness as compared with intravenous chemotherapy. The authors developed a high-performance liquid chromatography (HPLC) assay for the determination of tissue or plasma tegafur and 5-FU concentration in a single step extraction and a single HPLC injection. The retention times of 5-FU and tegafur were 5 and 16.5 minutes, respectively, and the internal standard retention times were 11.5 and 17.5 minutes for 5-bromouracil (5-BU) and beta-hydroxyethyltheophylline, respectively. The limit of quantification was 0.0125 microg/mL for 5-FU and 0.05 microg/mL for tegafur. The assay had good recovery (96.5% +/- 9.45% and 97.5% +/- 7.89% for 5-FU in plasma and tissue, respectively, and 88.5% +/- 12.17% and 104.9% +/- 8.77% for tegafur in plasma and tissue, respectively). Precision was good: the within-day and between-day standard deviation of the mean (RSD) for 5-FU (0.0125-5 microg/mL) and tegafur (0.5-150 microg/mL) was always <8%. The authors conclude that the method described here is ideally suited for the therapeutic monitoring of 5-FU and tegafur.

Simultaneous HPLC determination of 5-fluorouracil and its metabolites in plasma of cancer patients

5-Fluorouracil (5-Fu) is a commonly used anticancer agent for treatment of solid tumours. Certain studies have reported conflicting results between individual plasma concentration levels and toxicity or therapeutic effects. For this reasons some authors proposed to evaluate the plasma levels of 5-Fu metabolites 5-fluorouridine, 5-fluoro-2'-deoxyuridine and 5-fluoro-5,6-dihydro-uracil. The aim of the present work is to develop and validate a new HPLC method simultaneously determining 5-fluorouracil and its three metabolites, to be used to study the plasma levels, therapeutic effects and toxicity in cancer patients. The analytes were separated on a 4.6 x 250 mm ODS1 (5 micro m) not end-capped column, operating at room temperature. Elution was performed under isocratic conditions, employing a 1.5 mM K(3)PO(4) mobile phase (pH 5). 5-Bromo-5,6-dihydro-uracil was used as internal standard. The limits of quantitation were 0.5 micro g/mL for 5-fluorouracil, 1 micro g/mL for 5-fluoro-5,6-dihydro-uracil, 3 micro g/mL for 5-fluoro-2'-deoxyuridine and 5-fluorouridine; the stability, recovery, linearity, accuracy and specificity of the compounds were evaluated according to the criteria widely accepted. Using this method we measured plasma samples of 18 cancer patients treated with folinic acid (100 mg/m(2)) by intravenous administration, followed by an i.v. bolus of 5-Fu (400 mg/m(2)). The concentration levels of 5-fluorouracil and for 5-fluoro-5,6-dihydro-uracil were detectable in all the subjects while 5-fluorouridine and 5-fluoro-2'-deoxyuridine were present only in eight patients.

Determination of 5-fluorouracil and 5-fluoro-2'-deoxyuridine-5'-monophosphate in pancreatic cancer cell line and other biological materials using capillary electrophoresis

Capillary zone electrophoresis (CZE) was used for the rapid determination of 5-fluorouracil (5-FU) and 5-fluoro-2'-deoxyuridine-5'-monophosphate (FdUMP) in pancreatic cancer cell line (PANC-1), culture medium, plasma and pancreatic tissue. The assay is based upon protein precipitation with acetonitrile followed by a 9-min CZE analysis of the supernatant in an uncoated fused-silica capillary employing a borate buffer and on-column absorbance detection at 265 nm. Using 50 microl of sample, 5-FU levels between 4.12 and 132 microg/ml (31.7-1000 microM) were found to provide linear calibration graphs. Intra-day and inter-day RSD values evaluated from peak height ratios (n=5) were <7.6 and <8.8%, respectively. Corresponding RSD values of detection times (n=7) were <1 and <1.5%, respectively. The limits of detection for 5-FU and FdUMP were 1.72 and 5.29 microg/ml, respectively. As application, the accumulation of 5-FU by PANC-1 cells over a 4-h time period was investigated. Having a culture medium concentration of 100 microg/ml, the 5-FU cell content was estimated to become equal to that of the surrounding medium (i.e., 100 microg/ml or 3.61 fmol per cell with a volume of 4.7 pl) within that time period. The sensitivity of the assay was sufficient for the determination of 5-FU in all cell samples. FdUMP, however, could not be detected in these samples. Furthermore, the data obtained in uncoated capillaries are compared to those measured in a fused-silica capillary whose inner surface was coated with linear polyacrylamide (about 10-fold reduction of electroosmosis). The latter capillary format was found to be useless for simultaneous analysis of 5-FU and FdUMP in pancreatic cells but could be potentially useful for analysis of these compounds in plasma.

Simultaneous determination of flucytosine and fluorouracil in human plasma by high-performance liquid chromatography

A validated, sensitive and precise reversed-phase high-performance liquid chromatographic method for the simultaneous determination of 5-flucytosine (5-FC) and 5-fluorouracil (5-FU) in human plasma is described. Two compounds, 5-methylcytosine (5-MC) and 5-chlorouracil (5-CU), were used as internal standards for the determination of 5-FC and 5-FU, respectively. Plasma samples were deproteinized with trichloroacetic acid and chromatographed on an octylsilica column, maintained at 30 degrees C during elution, using a 0.04 M phosphate buffer, pH 7.0, as eleunt. Spectrophotometric diode array detection was used at 266 nm. 5-FC, 5-FU, 5-MC and 5-CU were found to have retention times of 4.8, 5.8, 7.7 and 11.0 min respectively. Recoveries of 91-120% with reproducibility and repeatability coefficients of variation of 0.8-6% were obtained. Mean correlation coefficients of 0.99989 and 0.9995 were found for the linear calibration curves (n = 2) of 5-FC (4.816-192.6 mg/l) and 5-FU (0.05368-5.368 mg/l), respectively. The limits of quantitation were 0.3 mg/l for 5-FC and 0.05 mg/l for 5-FU.

Simple and sensitive determination of 5-fluorouracil in plasma by high-performance liquid chromatography. Application to clinical pharmacokinetic studies

5-Fluorouracil (5-FU) is an antineoplastic agent widely employed in the treatment of many types of cancer. Recent studies have proved the need for individual adjustment of 5-FU dosage based on pharmacokinetics. A simple and sensitive high-performance liquid chromatographic method for the determination of 5-FU in plasma and their preliminary clinical pharmacokinetics is described. After sample acidification with 20 microl of orthophosphoric acid (5%), the drug is extracted from plasma using n-propanol-diethyl ether (16:84). The organic layer is evaporated to dryness, the residue dissolved in 100 microl of mobile phase and 20 microl of this mixture is injected into a LiChrospher 100RP-18 (5 microm, 250 x 4.0 mm) analytical column. Mobile phase consisted of potassium dihydrogenphosphate (0.05 M, adjusted to pH 3). The limit of quantitation was 2 ng/ml. The method showed good precision: the within-day relative standard deviation (RSD) for 5-FU (10-20,000 ng/ml) was 3.75% (2.57-5.93); the between-day RSD for 5-FU, in the previously described range, was 5.74% (4.35-7.20). The method presented here is accurate, precise and sensitive and it has been successfully applied for 5-FU pharmacokinetic investigation and therapeutic drug monitoring.

Determination of 5-fluorouracil in microvolumes of human plasma by solvent extraction and high-performance liquid chromatography

In the present study, a new reversed-phase HPLC method has been developed and validated for the quantitative determination of 5-fluorouracil (5-FU) in human plasma using only 100-microl samples. The sample extraction and clean-up procedure involved a simple liquid-liquid extraction after addition of 5-chlorouracil (5-CU), used as internal standard, with 5 ml ethyl acetate. Chromatographic separations were performed on an Inertsil ODS-3 column (250x4.6 mm ID; 5 microM particle size), eluted with a mobile phase composed of acidified water (pH 2.0). The column effluent was monitored by UV absorption measurement at a wavelength of 266 nm. The calibration curves were constructed over a range of 0.20-50.0 microM and were fitted by weighted (1/x) linear regression analysis using the ratio of peak heights of 5-FU and 5-CU versus concentrations of the nominal standards. Extraction recoveries over the total range averaged 92 and 93% for 5-FU and 5-CU, respectively. The lower limit of quantitation was established at 0.20 microM (approximately 26 ng/ml), with within-run and between-run precisions of 4.2 and 7.0%, respectively, and an average accuracy of 109.3%. The within-run and between-run precisions at four tested concentrations analyzed in quintuplicate over a time period of four days were < 1.4 and < 4.4%, respectively. The accuracy at the tested concentrations ranged from 98.4 to 102.3%. Compared to previously described validated analytical methods for 5-FU, our present assay provides equivalent to superior sensitivity, using only microvolumes of sample.

Simultaneous determination of 5-fluorouracil and uracil by high-performance liquid chromatography using four serial columns

A sensitive assay was developed for the quantitation of 5-fluorouracil (5-FU) and uracil using liquid-liquid extraction (LLE) and HPLC with UV detection. Analyses were performed with four microBondapak C18 columns connected in series using 20 mM acetic acid with 1% ACN as mobile phase. The calibration curves were linear across the range of 26-1000 ng ml(-1) (0.21-7.8 microM) for 5-FU and 1.0-14.0 microg ml(-1) (0.01-110 microM) for uracil. This assay has been implemented to determine the plasma concentrations for pharmacokinetic studies for 5-FU and uracil in conjunction with clinical trials.

Spectrophotometric and spectrofluorimetric determination of fluorouracil in the presence of its degradation products

Three reliable spectrophotometric and spectrofluorimetric procedures are described for the determination of fluorouracil in bulk powder and ampoules in the presence of its degradation products. One spectrophotometric procedure, based on measurement at 555 nm of the violet-coloured complex formed by fluorouracil with cobalt(II), has a detection limit of 0.03 mg mL(-1). Two sensitive spectrofluorimetric procedures are also proposed. One is based on measurement of the intrinsic fluorescence of the liberated fluorouracil at 375 nm, after precipitation as its cobalt(II) complex, decomposition of the precipitate with sulphuric acid and excitation at 295 nm. The second depends on excitation of the fluorouracil-cobalt(II) complex at 395 nm and measuring its fluorescence at 483 nm. The limits of detection of the two spectrofluorimetric procedures are 0.5 and 2 microg mL(-1), respectively. The three procedures have been used successfully for the determination of fluorouracil ampoules. The validity of the methods has been assessed by applying the standard addition technique.