Effect of Chlorpromazine on myocardial contractility and hemodynamics.

Hemodynamic effects of Chlorpromazine(CP) were studied in anesthetized open-chestdogs. Intravenous injection of 1.0mg/kg CP increased heart rate by 20.7 % , cardiac output by 14.7% , LVdp/dt/50 by 11.3% and QTc by 0.012, respectively. Systolic shortening of a segment of the heart muscle increased by 9.8% with decreases in end-diastolic length. These changes were inhibited completely by Propranolol and incompletely by Reserpine pretreatment. Blood pressure was lowered by CP, but no response to intravenous Methoxamine was observed 10 min after CP. However, with 10mg/kg of CP injected intravenously, heart rate and LVdp/dt/50 initially decreased markedly, and systolic shortening decreased in association with increases in end-diastolic length. Ten min later, the measurements increased above the control. These results suggested that CP has α-blocking and β-stimulating action mimicking an α(2)-blocker