The Pharmacokinetics And Drug Metabolism Study Of Indapamide

1. A sensitive and selective liquid chromatography-tandem mass spectrometric(LC/MS/MS) method for the determination of indapamide in human blood was developed. Indapamide and internal standard diphenhydramine were extracted from blood using liquid-liquid extraction, then separated on a Zorbax Extend C18 column(150×4.6 mm, I.D.5μm). The mobile phase consisted of methanol-water-formic acid (75:25:0.5, v/v/v), at a flow rate of 0.7 mL·min-1, the Thermo Finnigan TSQ Quantum Discovery tandem mass spectrometer equipped with atmospheric pressure chemical ionization(APCI) source was used as detector operated in the positive ion mode. Selected reaction monitoring(SRM) using the precursor to product ion combinations of m/z 366â†'m/z 132(indapamide)and m/z 256â†'m/z 167 (diphenhy dramine) was performed. The linear calibration curve was obtained in the concentration range of 5.0-600 ng·mL-1, the lower limit of quantification was 5.0 ng·mL-1. The determination of indapamide and internal standard was not affected by endogenous materials in blank blood, the intra-day and inter-day precision(RSD) was less than 13.5%, the accuracy was range from 98.7% to 105.4%. The method was successfully applied to the pharmacokinetic study for 18 healthy male volunteers given orally 5.0 mg indapamide tablets(test preparation) and indapamide tablets(reference preparation), and then the blood concentration was determined. The result indicates that the test and referene preparation are bioequivalent.2. A LC/MSn method was developed to study the drug metabolism of indapamide in rat, beegle dog and human first time. The mobile phase consisted of methanol-wate (40:60, v/v), at a flow rate of 0.5 mL·min-1, indapamide and it’s metablites were separated on a Zorbax Extend C18 column(150×4.6 mm, I.D.5μm). The agilent 1100 ion trap mass spectrometer equipped with electrospray ionization source(ESI) was used as detector operated in the negative ion mode, full scan, MS/MS and selective ion monitoring(SIM) were used. Eight metablites were found in rat, three metablites were found in beagle dog, three metablites were found in human, the species differences among rat, beegle dog and human were also compared.3. A LC/MS/MS method was developed to study the pharmacokinetics of indapamide in rat when indapamide was single used and combined with enalapril maleate. Indapamide and internal standard diphenhydramine were extracted from blood using liquid-liquid extraction, then separated on a Zorbax Extend C18 column(150×4.6 mm, I.D.5μm). The mobile phase consisted of methanol-water-formic acid (75:25:0.2, v/v/v), at a flow rate of 0.5 mL·min-1, The agilent 1100 ion trap mass spectrometer equipped with atmospheric pressure chemical ionization source was used as detector operated in the positive ion mode. Selected reaction monitoring using the precursor to product ion combinations of m/z 366â†'m/z 132(indapamide)and m/z 256â†'m/z 167(diphenhydramine) was performed. The linear calibration curve was obtained in the concentration range of 5.0-1500 ng·mL-1, the lower limit of quantification was 5.0 ng·mL-1. The determination of indapamide and internal standard was not affected by endogenous materials in blank blood, the intra-day and inter-day precision(RSD) was less than 10.1%, the accuracy was range from 95.7% to101.2 %. The method was successfully applied to the pharmacokinetic study for 12 wistar rats with 6 rats given orally indapamide of 0.5 mg·kg-1 and other 6 rats given orally indapamide of 0.5 mg·kg-1 and enalapril maleate of 2.0 mg·kg-1, and then the blood concentration was determined. The result indicates that the pharmacokinetic behavior of indapamide in rat is not affected by enalapril maleate when combined with enalapril maleate, drug combination won’t create antagonism, therefore the dosage of indapamide don’t have to change when combining with enalapril maleate.