DO SYNTHETIC ADRENERGIC AGENTS INTERFERE WITH THE MEASUREMENT OF ENDOGENOUS PLASMA-CATECHOLAMINE CONCENTRATIONS

Purpose: It is common to administer synthetic sympathomimetic and symp atholytic agents in the intensive care unit and operating room. The pr esent study examines whether such agents, as well as the products of c atecholamine metabolism, interfere with the quantitation of endogenous catecholamines by high-performance liquid chromatography. Methods: Sa mples of drugs and metabolites were assayed before and after alumina e xtraction and their relative retention times were compared with dopami ne, norepinephrine, and epinephrine relative retention times. Blood sa mples from patients receiving these drugs were also assayed for their interferences with catecholamine determination. Results: Phenylephrine interfered with the quantitation of epinephrine. Isoproterenol's peak was so delayed it appeared in the following chromatogram. Dobutamine had two small peaks in vitro, whereas in the patient samples only one peak was identified; the other was probably masked by the dopamine pea k. Labetalol had one peak when the pure drug was assayed but multiple peaks in patient samples, that were probably caused by metabolites of labetalol. Conclusion: Synthetic adrenergic agents and catecholamine m etabolites can potentially interfere with the quantitation of the endo genous catecholamines. Thus, it is important to examine whether such i nterference occurs when conducting high-performance liquid chromatogra phy assays.