Determination of Dobutamine in Plasma by Liquid Chromatography with Electrochemical Detection

Abstract

A simple, rapid and sensitive method for the analysis of dobutamine [useful clinically in patients with depressed cardiac function] in equine arterial and venous plasmas was developed. After the addition of an internal standard samples were extracted using disposable, prepacked reverse phase columns. Samples were chromatographed at room temperature over a 15 cm 3 .mu.m C-18 column. Detection was by a glassy carbon electrode operated at 0.55 volts with respect to Ag/AgCl electrode. Using this method sensitivities of 100 pg/ml (signal to noise; 3:1) were obtained. The applicability of the method is shown in anesthetized horses infused at 2.5, 5.0 and 0.5 .mu.g/kg per min. Dobutamine, .+-. 4-[2-[[3-(p-hydroxyphenyl)-1-methylpropyl]amino]ethyl]pyrocatechol is a synthetic catecholamine. Dobutamine has been useful clinically in patients with depressed cardiac function. Recently it has been used to increase cardiac output in shock patients. To investigate the pharmacokinetics and dose response in anesthetized horses, it was necessary to develop a rapid, simple and sensitive analytical method for measuring dobutamine in equine plasma. Dobutamine has been assayed by HPLC using fluorescence detection but lacks the sensitivity required for analysis of low dosage samples (1). Electrochemical detection of the catechol moiety of dobutamine provides both a sensitive and selective detection system.