SIMPLIFIED REVERSED-PHASE HPLC METHOD WITH SPECTROPHOTOMETRIC DETECTION FOR THE ASSAY OF VERAPAMIL IN RAT PLASMA

A high-performance liquid chromatographic (HPLC) method was developed for the assay of verapamil in rat plasma. After deproteinization of th e plasma sample with an acetonitrile-perchloric acid (8:2) mixture con taining dextromethorphan, the internal standard, an aliquot of the sup ernatant was directly analyzed on a cyanopropylsilane column with meth anol-acetonitrile-triethylamine acetate buffer (10:30:60) as the mobil e phase and detection at 235 mm. At a flow rate of 1.5 ml min(-1), a c omplete analysis was completed in less than 6 min. The method was line ar for verapamil concentrations in the range 0.5-10 mu g ml(-1) (r = 0 .9999). Recoveries for the same drug concentrations from spiked rat pl asma ranged from 85.6-93.0% (n = 8). The mean RSD values for intraday and interday assay reproducibility (n = 3) were, in both cases, less t han 0.9%. The limit of detectability was about 0.1 mu g ml(-1). The me thod was found useful to monitor the plasma levels of verapamil in rat s that had received this drug by the nasal, oral and intravenous route s of administration. (C) 1998 Elsevier Science B.V. All rights reserve d.