Development and validation of a sensitive LC–MS/MS assay for the quantification of nizatidine in human plasma and urine and its application to pharmacokinetic study

We developed and validated a high performance liquid chromatographic method coupled with triple quadrupole mass spectrometry for analysis of nizatidine in human plasma and urine. The biological samples were precipitated with methanol before separation on an Agilent Eclipse Plus C18 column (100 mm × 46 mm, 5 μm) with a mixture of methanol and water (95:5, plus 5 mM ammonium formate) as the mobile phase at 0.5 mL/min. Detection was performed using multiple reaction monitoring modes via electrospray ionization (ESI) at m/z 332.1 → 155.1 (for nizatidine) and m/z 335.1 → 155.1 (for [2H3]-nizatidine, the internal standard). The linear response range was 5–2000 ng/mL and 0.5–80 μg/mL for human plasma and urine, with the lower limits of quantification of 5 ng/mL and 0.5 μg/mL, respectively. The method was validated according to the biological method validation guidelines of the Food and Drug Administration and proved acceptable. This newly developed analytical method was successfully applied in a pharmacokinetic study following single oral administration of a 150 mg nizatidine capsule in to 16 healthy Chinese subjects. Maximum and endpoint concentrations in plasma and urine were quantifiable, suggesting our method is appropriate for routine pharmacokinetic analysis.