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 (MRM) 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 °C, three freeze–thaw cycles in 30 days and for 30 days under −70 °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) l, respectively; clearance rate (CL /F) were (1851.4 ± 496.9), (1596.2 ± 378.5) and (1894.2 ± 459.3) l/h, respectively; time to C max ( T max) were (1.00 ± 0.21), (1.05 ± 0.28) and (1.04 ± 0.16) 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 ± 0.85), (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 C