Abstract: AIM: To set up a method to determine the blood concentration of lansoprazole and its metabolites 5' -lansoprazole and lansoprazole sulphone.METHODS: The blood concentration of lansoprazole was determined by HPLC.RESULTS: Calibrated standard curve of lansoprazole in blood was Y=0.0136 +0.0012 X (r= 0.9994);the recoveries at three concentrations of 25, 200, and 2000 μg ·L ^-1 were 87.99 %, 94.38 %, and 77.21 %, respectively; and the RSD values were 7.79 %, 1.21 %, and 5.49 %, respectively.Calibrated standard curve of its metabolite 5' -OH lansoprazole in plasma was Y=0.0025 +0.000926 X (r=0.9990). The recoveries at three concentrations (20, 100, and 500 μg·L ^-1)were 85.85 %, 87.64 %, and 107.70 %, respectively;and the RSD values were 10.73 %, 6.98 %, and 5.62 %, respectively.Calibrated standard curve of another metabolite lansoprazole sulphone in plasma was Y=0.01486 +0.001462X (r=0.9995), the recoveries at three concentrations (20, 100, and 1000 μg ·L ^-1) were 79.84 %, 85.18 %, and 100.68 %;respectively; and the RSD values were 9.22 %, 2.36 %, and 4.81 %, respectively.After 30 mg of lansoprazole was administered by a volunteer po, the values of C_max of 5' - OH lansoprazole, lansoprazole, and lansoprazole sulphone were 113.21, 1561.54, and 131.14 mg·L ^-1, respectively.CONCLUSION: The method is accurate for determining the blood concentration of lansoprazole and its metabolites 5' -lansoprazole and lansoprazole sulphone.

Key words: pharmacology, lansoprazole, plasma concentration, HPLC