Automated determination of 5-fluorouracil and its metabolite in urine by high-performance liquid chromatography with column switching

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.

Feasibility of measuring 5-fluorouracil catabolic potential by oral loading

The efficacy of 5-fluorouracil (5-FU) treatment and the incidence of adverse events differ among patients and depend to some extent on individual variations in drug catabolism. This feasibility study aimed to determine the optimum conditions for a 5-FU oral load test, which would allow the simple evaluation of individual differences in 5-FU catabolism. Patients with colon cancer were given oral 5-FU (200 mg/day) for 3 days (n = 36) or a single 100 mg dose (n = 14). Serum concentrations of uracil, dihydrouracil, 5-FU and 5-fluoro-5,6-dihydrouracil were measured before and after 5-FU administration. The results suggested that a decline in 5-FU metabolism was associated with continuous administration and increasing age. We conclude that a continuous load of 5-FU is necessary in order to predict the efficacy and side-effects of the drug. The 3-day regimen, with its ease of administration, merits further study to assess its possible clinical application.

An accurate dihydrouracil/uracil determination using improved high performance liquid chromatography method for preventing fluoropyrimidines-related toxicity in clinical practice

An accurate and improved HPLC method was set up to measure both dihydrouracil (UH2) and uracil (U) in plasma, and to assess their ratio. Analytes retention time, separation and peak purity were greatly optimized with a Hypercarb column and a diode array detector. U and UH2 limits of quantification were 1.25 and 0.625 ng/mL. U and UH2 within-day precisions were 0.9-2.3% and 0.7-5.6%. Between-day precisions were 1.3-5.3% and 1.3-7.1%. Accuracy was 0.1-6.1%. UH2/U ratio between-day variability was low, but ratio decreased from 02:00 p.m. This method is now used in practice to detect patients at risk of fluoropyrimidine toxicity and to individually adapt the dosage.

Rapid determination of 5-fluorouracil in plasma using capillary electrophoresis

A rapid, simple and sensitive capillary electrophoresis (CE) method used for the determination of 5-fluorouracil in rabbit plasma is described in the present paper. In this method, samples were simply pretreated by a solvent extraction procedure prior to injection. With a running buffer composed of 30 mM Tris-H(3)PO(4) (pH 7.0) and 5% isopropanol, 5-fluorouracil was easily separated from the external standard alpha-phenethylol as well as other substances existed in the plasma. A linearity of 5-fluorouracil was determined in the range from 0.17 to 42.50 microg/ml with a correlation coefficient of 0.999. A limit of quantitation (LOQ) corresponding to signal-to-noise ratio of 10 was obtained (LOQ=0.08 microg/ml). The method was successfully used for determining the 5-fluorouracil in real plasma samples from rabbits.