Objective: To investigate the pharmacokinetics of baicalin in rats after oral administration of Qingyan Lige pills by HPLC-MS-MS. Method: With luteolin as the internal standard (IS)

the analysis was carried out on a ZOBAX SB-C18 (2.1 mm×50 mm

3.5 μm) column using acetonitrile-0.2% formic acid (24 ：76) as the mobile phase. The detection was performed by means of electrospray ionization (ESI) mass spectrometry in positive ion mode with multiple reaction monitoring (MRM). Quantification was performed using the transitions of m/z 447.1→270.9 for baicalin

m/z 286.9→152.9 for IS. Result: After oral administration of Qingyan Lige pills to SD rats

the Tmax of baicalin was 2.4 h

the Cmax was 0.59 mg·L-1

the AUC0~∞ was 2.80 mg·L-1·h and the t1/2 was 8.24 h. The plasma concentration-time curve exhibited double peak

which indicated that baicalin may have hepatoenteral circulation in vivo. Conclution: The method described in this report has high sensitivity and selectivity. The results of pharmacokinetic study on baicalin would be a suitable reference in clinical application for Qingyan Lige pills.