Development and validation of a rapid and sensitive HPLC method for the quantification of 5‐fluorocytosine and its metabolites

To study the intracellular metabolism of the prodrug 5‐fluorocytosine (5FC), we developed a novel reverse‐phase high‐performance liquid chromatography method to simultaneously detect 5FC and its four major anabolic metabolites: 5‐fluorouracil, 5‐fluorouridine, 5‐fluorouridine‐monophosphate and 5‐fluoro‐2′deoxyuridine‐5′‐monophosphate. Separation of each compound was accomplished under isocratic conditions using a C₁₈ column and mobile phase of formic acid–water (1 : 99 v/v). The method was validated for both accuracy and reproducibility in cell culture media. Additionally, metabolites were assessed for stability at ambient temperatures and following freeze–thaw cycles. Calibration curves were linear over a range of 1–200 μg/mL. Limit of quantification for four of the five compounds was 1 μg/mL in cell culture media (RSD < 11%). This method was successfully used to monitor intracellular conversion of 5FC to its metabolic products over a 24h period. Copyright © 2009 John Wiley & Sons, Ltd.