Alessi-Severini S, Coutts R T, Jamali F, Pasutto F M
Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Canada.
J Chromatogr. 1992 Nov 6;582(1-2):173-9. doi: 10.1016/0378-4347(92)80316-i.
Methocarbamol enantiomers in rat and human plasma were quantified using a stereospecific high-performance liquid chromatographic method. Racemic methocarbamol and internal standard, (R)-(-)-flecainide, were isolated from plasma by a single-step extraction with ethyl acetate. After derivatization with the enantiomerically pure reagent (S)-(+)-1-(1-naphthyl)ethyl isocyanate, methocarbamol diastereomers and the (R)-flecainide derivative were separated on a normal-phase silica column with a mobile phase consisting of hexane-isopropanol (95:5, v/v) at a flow-rate of 1.6 ml/min. Ultraviolet detection was carried out at a wavelength of 280 nm. The resolution factor between the diastereomers was 2.1 (alpha = 1.24). An excellent linearity was observed between the methocarbamol diastereomers/internal standard derivative peak-area ratios and plasma concentrations, and the intra- and inter-day coefficients of variation were always < 9.8%. The lowest quantifiable concentration was 0.5 microgram/ml for each enantiomer (coefficients of variation of 9.8 and 8.8% for (S)- and (R)-methocarbamol, respectively), while the limit of detection (signal-to-noise ratio 3:1) was approximately 10 ng/ml. The assay was used to study the pharmacokinetics of methocarbamol enantiomers in a rat following intravenous administration of a 120 mg/kg dose of racemic methocarbamol and to evaluate plasma and urine concentrations in a human volunteer after oral administration of a 1000-mg dose of the racemate. The method is suitable for stereoselective pharmacokinetic studies in humans as well as in animal models.
采用立体专一性高效液相色谱法对大鼠和人血浆中的美索巴莫对映体进行定量分析。外消旋美索巴莫和内标物（R）-（-）-氟卡尼通过用乙酸乙酯一步萃取从血浆中分离出来。用对映体纯试剂（S）-（+）-1-（1-萘基）乙基异氰酸酯衍生化后，美索巴莫非对映体和（R）-氟卡尼衍生物在正相硅胶柱上分离，流动相为己烷-异丙醇（95:5，v/v），流速为1.6 ml/min。在280 nm波长处进行紫外检测。非对映体之间的分离度因子为2.1（α = 1.24）。美索巴莫非对映体/内标衍生物峰面积比与血浆浓度之间呈现出良好的线性关系，日内和日间变异系数始终<9.8%。每种对映体的最低可定量浓度为0.5微克/毫升（（S）-和（R）-美索巴莫的变异系数分别为9.8%和8.8%），而检测限（信噪比3:1）约为10纳克/毫升。该测定法用于研究大鼠静脉注射120毫克/千克剂量的外消旋美索巴莫后美索巴莫对映体的药代动力学，并评估一名人类志愿者口服1000毫克外消旋体剂量后血浆和尿液中的浓度。该方法适用于人类以及动物模型的立体选择性药代动力学研究。
