Background: Extensive therapeutic drug monitoring needs an analytical method for efficient and sensitive quantification of analytes of interest in clinical pharmacology.

Objectives: A rapid, robust, sensitive and simple UPLC-MS/MS method to quantify Methsuximide (Ms) and N-desmethyl methsuximide/Normesuximide (MsMET) in human plasma was optimized, developed, and validated for application in a pharmacokinetic study.

Methods: Reverse phased chromatography was performed using Zorbax SB-C18, 4.6 x 75 mm., 3.5 μm as stationary phase, methanol and 0.1% formic acid (60:40 v/v) as mobile phase which was delivered isocratically at a flow rate of 0.9 mL/min. The sample injection volume was 5 μL. Mass spectrometric quantification of the analytes was performed using positive electrospray ionization as mass interface along with multiple reaction monitoring (MRM) as acquisition mode.

Results: The selected mass transition ions for analyte, metabolite and its respective internal standards are as follows, precursor ion (m/z) and product ion (m/z): Ms (204.06 and 119.02), MsMET (190.05 and 119.82), Ms internal standard (MsIS) (209.17 and 124.02), and MsMET internal standard (MsMETIS) (195.09 and 124.16), respectively. The current method was found to be linear for Ms (60.720-6043.800 ng/mL) and MsMET (60.389 - 6010.800 ng/mL) with r2 values not less than 0.999. The mean recoveries of all analytes ranged between 71.37 and 86.38 percentage. Conclusion: This method was validated in accordance with USFDA’s bioanalytical guidelines.

This method could be applied for a routine analysis of Ms and MsMET in clinical pharmacological practice.

背景：广泛的治疗药物监测需要一种分析方法，以对临床药理学中感兴趣的分析物进行有效和灵敏的量化。

目标：优化、开发并验证了一种快速、稳健、灵敏且简单的 UPLC-MS/MS 方法，用于量化人血浆中的甲琥胺 (Ms) 和 N-去甲基甲磺酰亚胺/去甲嘧啶 (MsMET)，以用于药代动力学研究。

方法：使用 Zorbax SB-C18, 4.6 x 75 mm., 3.5 μm 作为固定相，甲醇和 0.1% 甲酸 (60:40 v/v) 作为流动相进行反相色谱，以等度流速输送0.9 毫升/分钟。进样量为 5 μL。使用正电喷雾电离作为质量界面以及多反应监测 (MRM) 作为采集模式对分析物进行质谱定量。

结果：分析物、代谢物及其各自内标的选定质量转换离子如下，母离子 (m/z) 和产物离子 (m/z)：Ms（204.06 和 119.02），MsMET（190.05 和 119.82）， Ms 内标 (MsIS)（209.17 和 124.02）和 MsMET 内标（MsMETIS）（195.09 和 124.16）。发现当前方法对 Ms (60.720-6043.800 ng/mL) 和 MsMET (60.389 - 6010.800 ng/mL) 呈线性，r2 值不小于 0.999。所有分析物的平均回收率介于 71.37 和 86.38% 之间。结论：该方法已根据 USFDA 的生物分析指南进行了验证。

该方法可用于临床药理实践中对 Ms 和 MsMET 的常规分析。