Extended application of an LC–MS/MS method for the analysis of vesnarinone and its metabolites in human urine and dialysate fluid

Vesnarinone, a positive inotropic drug developed for congestive heart failure, and its metabolites (OPC-8230, OPC-18136, OPC-18137) were analyzed in human dialysate and urine (plus an additional metabolite: OPC-18692 in urine) samples using a modification to a previously published LC–MS/MS assay for the analysis of human plasma and urine samples. OPC-8192, a structural analogue of vesnarinone, was used as the internal standard. The analytes of interest were extracted from human dialysate or urine by a solid phase extraction method using a pre-conditioned C-18 extraction column. The analytes were then resolved by a 7 min gradient elution on a reverse phase high performance liquid chromatographic column. Vesnarinone and metabolites were detected on a PE/Sciex API III+Biomolecular Mass analyzer in MS/MS mode using a Turbo IonSpray interface. The linear range of quantitation in dialysate was 2.00–100.00 ng/ml for vesnarinone and 0.50–25.00 ng/ml for each metabolite. In urine, the linear range was of 0.50–25.00 μg/ml for vesnarinone and 0.10–5.00 μg/ml for the metabolites. This method was used to support the analysis of urine and dialysate samples from renally impaired patients who are on vesnarinone treatment.