Improved analysis of 5-Fluorouracil and 5,6-dihydro-5-Fluorouracil by HPLC with diode array detection for determination of cellular dihydropyrimidine dehydrogenase activity and pharmacokinetic profiling

• Published in: Therapeutic drug monitoring Vol. 27; no. 3; p. 362
• Main Authors: Di Paolo, Antonello, Danesi, Romano, Ciofi, Laura, Vannozzi, Francesca, Bocci, Guido, Lastella, Marianna, Amatori, Federica, Martelloni, Bianca Maria, Ibrahim, Toni, Amadori, Dino, Falcone, Alfredo, Del Tacca, Mario
• Format: Journal Article
• Language: English
• Published: United States 01.06.2005
• Subjects: Aged; Antimetabolites, Antineoplastic - blood; Chromatography, High Pressure Liquid; Dihydrouracil Dehydrogenase (NADP) - metabolism; Drug Monitoring; Female; Fluorouracil - blood; Fluorouracil - pharmacokinetics; Humans; Male; Middle Aged; Uracil - analogs & derivatives; Uracil - blood
• ISSN: 0163-4356
• DOI: 10.1097/01.ftd.0000162016.11148.1b

Administration of 5-fluorouracil (5-FU) may be associated with severe toxicities in patients who are deficient of dihydropyrimidine dehydrogenase (DPD) activity. For this reason, a sensitive HPLC method for the analysis of 5-FU and 5-fluoro-5,6-dihydrouracil (5-FDHU) was developed in the present study for the determination of DPD activity in nucleated cells of peripheral blood and pharmacokinetic analysis of 5-FU and 5-FDHU in humans. 5-FU and 5-FDHU were extracted from biologic matrices by adding sodium acetate, sodium sulfate, and diethyl ether/propanol. Dried samples were reconstituted in a mobile phase (KH2PO4 35 mmol/L, pH 4.0), isocratically eluted with a Hypersil C18 stationary phase (25 cm x 4.6 mm, 10 microm), and detected by a diode array detector (measurement and reference wavelengths, 215 and 360 nm, respectively). 5-Fluorocytosine (internal standard), 5-FDHU, and 5-FU were eluted within 13 minutes of the injection without interferences. Recoveries ranged between 81% to 85% for all compounds, and the method proved to be linear, with a coefficient of linearity of 0.999. The limits of detection and quantification were 3.2 and 16 ng/mL, respectively, and the within-day and between-day CV were less than 10% for both 5-FU and 5-FDHU. The present assay proved to be sufficiently sensitive and specific to evaluate cellular DPD activity and measure 5-FU and 5-FDHU plasma concentrations in cancer patients, thus allowing therapeutic 5-FU monitoring in patients and identification of DPD-deficient subjects at major risk of severe toxicities.