Simultaneous determination of verapamil and its major metabolite in human plasma by high performance liquid chromatography
Tan, L.; Yang, S.R.; Liu, X.Q.; Yuan, Y.S.
Yao Xue Xue Bao 30(9): 689-693
1995
ISSN/ISBN: 0513-4870 PMID: 8701745 Document Number: 453861
A sensitive high-performance liquid chromatographic assay suitable for the simultaneous determination of verapamil (I) and its major active metabolite norverapamil (II) in human plasma is described. After adding internal standard ethmosine, plasma samples were extracted using a mixture of n-hexane and n-butyl alcohol (12:1) to give mean recoveries of gt 92% of both I, and II. The extracts were chromatographed on a C-18 reversed phase column with a mobile phase composed of methanol, water and triethylamine (67: 33 : 0.4, pH 6.7), with UV (lambda, 279 nm) detection. The calibration curves' were linear over a wide range of concentrations ( 25 apprx 10000 ng cntdot ml-1), and the limits of determination was 2.5 ng cntdot ml-1 for I and 5.0 ng cntdot ml-1 for II. The method showed good precision: the within-day RSD were lt 7. 6% for both I and II; the day-to-day RSD were lt 8.6% for both I and II. Using this assay, plasma concentrations of both I and II were simultaneously determined in six volunteers after a single oral dose of 120 mg of verapamil cntdot HCl.