Effects of changes in the doxapram HCl concentration in the blood on the cardiac conduction system

Abstract

We studied the effect of doxapram HCl on the cardiac conduction system in the adult Wister rats under urethane anesthesia. ECG and respiratory movements were recorded by Biopac MP-30 system. The doxapram HCl was intravenously injected and blood samples were obtained at 5, 15, 30 and 45 min. after the injection. The concentration of the drug was measured with the high performance liquid chromatography. The effect of the drug on RR, PR and QT intervals of ECG was evaluated in two groups of rats with and without preadministration of atropine. The cardiac conduction velocity was analyzed with Fluclet program. The concentration of doxapram HCl in the blood showed the maximum value at 5 min. after injection of the drug and decreased gradually in progress of time. Administration of the atropine sulfate reduced RR interval and PR interval without any change in QT interval. On the other hand administration of the doxapram HCl prolonged QT and PR interval but reduced RR interval. The effect of the drug depended on concentration. The results suggest that the doxapram HCl affect the repolarization of the ventricle as well as atrioventricular conduction. [J Physiol Sci. 2007;57 Suppl:S208]