DETERMINATION OF THE FLUORESCENT DRUGS DIPYRIDAMOLE AND BENZYDAMINE IN RAT PLASMA BY LIQUID-CHROMATOGRAPHY WITH PEROXYOXALATE CHEMILUMINESCENCE DETECTION

A facile and sensitive method for the determination of the fluorescent drugs dipyridamole (coronary vasodilator) and benzydamine hydrochloride (anti-inflammatory) in rat plasma is presented. The method consists of the addition of an internal standard (DNS-L-phenylalanine for dipyridamole and dipyridamole for benzydamine hydrochloride), deproteinization of plasma (1-mu-l for dipyridamole and 10-mu-l for benzydamine hydrochloride) with 13 volumes of acetonitrile, direct injection of the supernatant into an ODS column, separation by liquid chromatography and peroxyoxalate chemiluminescence detection using bis[4-nitro-2-(3,6,9-trioxadecyloxycarbonyl)phenyl] oxalate and hydrogen peroxide. Calibration graphs were linear over the ranges 2.5-200 nM and 2.5-100-mu-M for dipyridamole and benzydamine hydrochloride in plasma, respectively. The detection limits (signal-to-noise ratio = 2) were 345 pM for dipyridamole and 147 nM for benzydamine hydrochloride in plasma. The relative standard deviation for four determinations of dipyridamole at 2.5 nM and benzydamine hydrochloride at 2.5-mu-M in plasma were 3.7% and 2.6%, respectively. The method was applied to real samples and the time courses of the plasma concentration after oral administration of the two drugs [0.50 mg kg-1 (0.99-mu-mol kg-1) and 10 mg kg-1 (29-mu-mol kg-1), respectively] were obtained.