Rapid analysis of verapamil in plasma by reversed phase HPLC

A modified and simple HPLC procedure has been developed for verapamil in plasma. Plasma samples have been vortex-mixed and centrifuged without any need of extraction. The analysis has been performed on a C20 reversed-phase column with fluorometric detection using 5,6-benzoquinoline as an internal standard. Standard curve has been found to be linear for concentrations from 30 to 1000 ng/ml (plasma) for verapamil and no potential source of interference was present. The method has the advantages of speed, small sample requirement and reproducibility. Applicability of the method has been demonstrated by a pharmacokinetic study in 7 rabbits which received a single dose of 0.25 mg verapamil hydrochloride by intravenous administration.