'Shemnai' injection is derived from traditional Chinese medicine 'Shenmaisan' and made from Radix ginseng Rubra and Radix Ophiopogonis. Ginsenoside-Rg(1), as a major constituent of Radix ginseng Rubra, is considered responsible for the efficacy of this injection. A rapid, simple and accurate method has been established for determination of ginsenoside-Rg(1) in Shenmai injection and human plasma using LG-ESI-MS/MS, and to study the pharmacokinetics of Rg(1) in ten healthy volunteers after intravenous single dosing of 60 nil, of Shenmai injection. Following solid-phase extraction (SPE), samples were separated on a C, column coupled with electrospray ionization mass spectrometry. The protonated analyte was quantified by multiple reaction monitoring (MRM) with a quadruple mass spectrometer in positive mode. Linearity was confirmed in the concentration range of 1 to 1000 ng/mL for Rg(1), and the lower limit of quantification (LLOQ, S/N > 10) was I ng/mL. The intraday and interday RSDs were within 15% and mean extraction recoveries ranged from 98.6% to 104.9%. The pharmacokinetics of Rg(1) in healthy volunteers conforms to the two-compartment open model. The main pharmacokinetics parameters were as follows: t(1/2 beta), 2.09 +/- 1.89 h; CL, 0.03 +/- 0.01 L kg(-1) h(-1); AUC (0 similar to infinity), 124.4 +/- 35.9 2 ng mL(-1) h and AUC (0 similar to infinity), 127.9 +/- 37.2 ng mL(-1) h, respectively. Copyright (c) 2008 John Wiley & Sons, Ltd.