Simultaneous high-performance liquid chromatographic determination of SCH 59884 (phosphate ester prodrug of SCH 56592), SCH 207962 and SCH 56592 in dog plasma.

SCH 59884 is an IV prodrug of SCH 56592, the broad-spectrum azole antifungal agent that is active both orally and intravenously in animal models of infection. SCH 56592 is in phase III clinical trials for the treatment of serious systemic fungal infections. SCH 59884 is a carboxylate ester of SCH 56592 with gamma-butyric acid phosphate. Following IV administration of SCH 59884, the compound is rapidly dephosphorylated to SCH 207962 which is then hydrolyzed to SCH 56592. A high-performance liquid chromatographic (HPLC) method was developed for the simultaneous determination of SCH 59884, SCH 207962 and SCH 56592 in plasma of dogs, a species used for safety evaluation. The HPLC analysis involved protein precipitation with methanol followed by separation on a C-18 column and quantitation by UV absorbance at 260 nm. The lower limits of quantification were 0.1 microg/ml for SCH 59884 and 0.05 microg/ml for SCH 207962 and SCH 56592 in dog plasma. The linearity for the three compounds was satisfactory as indicated by correlation coefficients (r) of >0.98, back-calculated concentrations and visual examination of the calibration curves. The precision and accuracy were satisfactory as shown by coefficients of variation (CV) ranging from 2.4 to 10.6%, and bias values ranging from -8.4 to 13.3%. Moreover, SCH 59884 and SCH 207962 were stable in dog plasma after being subjected to three freeze-thaw cycles. SCH 56592 had been shown earlier to be stable under these conditions. The assay was shown to be specific, accurate, precise, and reliable for use in pharmacokinetic and toxicokinetic studies.