Determination of tegaserod by LC-ESI-MS/MS and its application to a pharmacokinetic study in healthy Chinese volunteers

A simple, rapid and sensitive high performance liquid chromatography-electrospray ionization-tandem mass spectrometry (HPLC-ESI-MS/MS) assay for determination of tegaserod in human plasma using diazepam as internal standard (IS) was established. After adjustment to a basic pH with sodium hydroxide, plasma was extracted by ethyl acetate and separated by high performance liquid chromatography (HPLC) on a reversed-phase C-18 column with a mobile phase of methanol: 5 mM ammonium acetate (75:25, v/v, adjusting the pH to 3.5 with glacial acetic acid). The quantification of target compounds was obtained by using multiple reaction monitoring (NIRM) transitions; m/z 302.5, 173.2 and 285.4, 193.2 were measured in positive mode for tegaserod and internal standard (diazepam), respectively. The lower limit of quantification (LLOQ) was 0.05 ng/ml. The calibration curves were linear over the range 0.05-8.0 ng/ml (r = 0.9996) for tegaserod. The mean absolute recovery of tegaserod was more than 85.56%. Intra- and inter-day variability values were less than 9.21% and 10.02%, respectively. The samples were stable for 8 h under room temperature (25 degrees C, three freeze-thaw cycles in 30 days and for 30 days under -70 degrees C). After administration of a single dose of tegaserod maleate 4 mg, 6 mg and 12 mg, respectively, the area under the plasma concentration versus time curve from time 0 h to 12 h (AUC(0-12)) were (2.89 +/- 0.88), (5.32 +/- 1.21) and (9.38 +/- 3.42) ng h/ml, respectively; peak plasma concentration (C-max) were (1.25 +/- 0.53), (2.21 +/- 0.52) and (4.34 +/- 1.66) ng/ml, respectively; apparent volume of distribution (V-d/F) were (6630.5 +/- 2057.8), (7615.2 +/- 2242.8) and (7163.7 +/- 2057.2) 1, respectively; clearance rate (CL/F) were (1851.4 +/- 1496.9), (1596.2 +/- 378.5) and (1894.2 +/- 459.3) 1/h, respectively; time to C-max (T-max) were (1.00 +/- 0.21), (1.05 +/- 0.28) and (1.04 +/- 10.16) h, respectively; and elimination half-life (t(1/2)) were (3.11 +/- 0.78), (3.93 +/- 0.92) and (3.47 +/- 0.53) h, respectively; MRT were (3.74 +/- 10.85), (4.04 +/- 0.56) and (3.28 +/- 0.66) h, respectively. The essential pharmacokinetic parameters after oral multiple doses (6 mg, b.i.d) were as follows: C-ssmax (2.72 +/- 0.61) ng/ml; T-max (1.10 +/- 0.25) h; C-ssmin (0.085 +/- 0.01) ng/ml; C-av (0.54 +/- 0.12) ng/ml; DF, (4.84 + 0.86); AUC(ss), (6.53 +/- 1.5) ng h/ml. This developed and validated assay method had been successfully applied to a pharmacokinetic study after oral administration of tegaserod maleate in healthy Chinese volunteers at a single dose of 4 mg, 6 mg and 12 mg, respectively. The pharmacokinetic parameters can provide some information for clinical medication. (c) 2007 Elsevier B.V. All rights reserved.