Arrhythmogenic, Antiarrhythmic and Inotropic Properties of Opioids

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Abstract
Since the effects in the intact organism are complicated by central as well as peripheral effects, we compared the direct cardiac effects of three commonly used opioids on isolated heart muscle. Concentration-response curves for electrophysiological and inotropic effects of piritramide, pethidine and morphine (10-6-10-4 mol/l) on spontaneously beating and electrically stimulated rat atria were obtained. Piritramide decreased spontaneous frequency, induced arrhythmia and cardiac arrest. It had no significant effect on effective refractory period and electrical threshold for excitation, but decreased contractile force. Pethidine increased effective refractory period, had no effect on electrical threshold and increased contractile force. Morphine induced no significant electrophysiological effects, but decreased contractile force slightly. These results indicate direct negative chronotropic and arrhythmogenic actions of piritramide, possible class III antiarrhythmic action of penthidine and lack of major direct cardiac effects of morphine.