Objective To study the pharmacokinetics of nitidine chloride(NC) in rat plasma after intragastrical(i.g.) administration. Methods A liquid chromatography-electrospray ionization-mass/mass sprectrometry(LC-ESI-MS/MS) was used and carbamazepine was used as an intermal standard(I.S.). The rat plasma samples were deproteinized with acetonitrile and the resultant supernatant was assayed on an analytical Diamonsil ~(TM)ODS C_(18) column(2.1 mm × 150 mm) equipped with a C_(18) guard column(4 mm × 20 mm) with a mobile phase of acetonitrile–10 mM ammonium acetate buffer–formic acid(35: 65: 0.2, v/v/v) at the flow rate of 0.25 mL/min. The LC–MS was carried out on a triple-quadrupole mass spectrometry equipped with an ESI and positive selected-ion monitoring. Target ions were monitored at [M-Cl]~+ m/z 348.2 for NC and [M + H]~+ m/z237.2 for I.S., respectively. Results The simple one step deproteinize and rapid analysis method were successfully used in pharmacokinetic study on NC after i.g. administration. The linear relationship was good over the range of 2.5 – 1000.0 ng/ml(r~2 = 0.999 2) in rat plasma. The lower limit of quantification and detection were 2.5 and 1.6 ng/ml, respectively. The extraction recovery was in the range of 86.54 – 98.60%. The intra-and inter-day precisions(relative standard deviation) were less than 6.00%, with accuracies deviation between 89.40 to 95.57%. A two-compartment pharmacokinetic open model was proposed and validated to explain the apparent biphasic disposition of NC in rat plasma after i.g. administration. Conclusion This study was successfully applied to a pharmacokinetic study of NC in rats plasma following i.g. administration and could be used for preclinical and clinical pharmacokinetic evaluation of NC. Objective To study the pharmacokinetics of nitidine chloride (NC) in rat plasma after intragastrical (ig) administration. Methods A liquid chromatography-electrospray ionization-mass / mass sprectrometry (LC-ESI-MS / MS) was used and carbamazepine was used as an The rat plasma samples were deproteinized with acetonitrile and the resultant supernatant was assayed on an analytical Diamonsil (TM) ODS C 18 column (2.1 mm × 150 mm) equipped with a C 18 guard column (4 mm × 20 mm) with a mobile phase of acetonitrile-10 mM ammonium acetate buffer-formic acid (35: 65: 0.2, v / v / v) at the flow rate of 0.25 mL / Target ions were monitored at [M-Cl] ~ + m / z 348.2 for NC and [M + H] ~ + m / z 237. 2 for IS, respectively. Results The simple one step deproteinize and rapid analysis method were successfully used in pharmacokinetic study on NC after ig The linear relationship was good over the range of 2.5 - 1000.0 ng / ml (r ~ 2 = 0.999 2) in rat plasma. The lower limit of quantification and detection were 2.5 and 1.6 ng / ml, respectively. The extraction recovery were in the range of 86.54-98.60%. Both intra-and inter-day precisions (relative standard deviation) were less than 6.00%, with accuracies deviation between 89.40 and 95.57%. A two-compartment pharmacokinetic open model was proposed and validated to explain the apparent biphasic disposition of NC in rat plasma after ig administration. Conclusion This study was successfully applied to a pharmacokinetic study of NC in rats plasma and ig be used for preclinical and clinical pharmacokinetic evaluation of NC.