AIM To develop a
HPLC-MS for the determination of enalapril and its metabolite
enalaprilat in human
plasma and to investigate the
pharmacokinetics of the enalapril tablet in human.METHODS After being mixed with the internal standard benazepril,plasma samples were deproteinized and separated by HPLC on a reversed-phase C_(18) column with a mobile phase of methanol-0.1% formic acid water solution(66∶34,V/V).LC-ESI-MS was performed in the selected ion monitoring(SIM) mode using target ions at m/z 377.4 for enalapril,m/z 349.3 for enalaprilat and m/z 425.4 for internal standard.The fragmentor voltage was 80 V.A single oral dose of 20 mg enalapril was administered to 20 helthy volunteers.RESULTS Calibration curves for enalapril and enalaprilat were linear over the range of 1-300 μg·L~(-1).The RSD of intra-day were both less than 3.2 % for enalapril and enalaprilat.The RSD of inter-day were less than 7.0 % and 11.3 % for enalapril and enalaprilat,respectively.For enalapril,the
main pharmacokinetic parameter t_(1/2),t_(max),and ρ_(max) were(1.5±0.4)h,(0.8±0.2)h,(222.9±57.6)μg·L~(-1),respectively.For enalaprilat,the main pharmacokinetic parameter t_(1/2),t_(max),and ρ_(max) were(10.1±2.6)h,(3.5±0.9)h,(86.51±44.8)μg·L~(-1),respectively.CONCLUSION The assay was proved to be sensitive,accurate and convenient.It can be applied to study the pharmacokinetics and bioavailability of enalapril and enalaprilat formulations in humans.
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