Simultaneous determination of lercanidipine, benazepril and benazeprilat in plasma by LC-MS/MS and its application to a toxicokinetics study.

We aim to develop a rapid, simple, sensitive and specific LC-MS/MS method for the simultaneous quantification of lercanidipine, benazepril and benazeprilat in plasma. It is performed on the Agilent 6410 LC-MS/MS under the multiple-reaction monitoring (MRM) mode with electrospray ionization. Gliclazide was used as the internal standard (IS). Analytes and IS were extracted from plasma by solid-phase extraction. The reconstituted samples were chromatographed on a Diamond C₁₈(150 mm × 4.6 mm, 5 μm) column. The mobile phase was composed of 0.1% acetic acid-acetonitrile (50:50, v/v), with gradient flow rates: 0.6 mL/min (0-4.55 min); 4.55-4.65 min, 1 mL/min; 1 mL/min (4.65-9.5 min); 9.5-9.6 min, 0.6 mL/min; 0.6 mL/min (9.6-10 min). Method validation demonstrated that the method was of satisfactory specificity, sensitivity, precision and accuracy in linear ranges of 1-2000 ng/mL for lercanidipine, 1-2000 ng/mL for benazepril and 1-1600 ng/mL for benazeprilat, respectively. The precision (RSD%) was better than 15, and the lower limit of quantitation was identifiable and reproducible at 1 ng/mL for the three analytes. The plasma samples were stable after being stored for more than 60 days and after two freeze-thaw cycles (-20 to -25 °C). It is demonstrated that this method was successfully applied to samples from a toxicokinetics study of a compound of lercanidipine and benazepril in beagle dogs.