A Clinical Study of Mechanisms of Action of Chlorpromazine

• The effects of chlorpromazine as part of the premedication for surgical anesthesia were studied in 3,500 cases, including 1,450 cases of spinal anesthesia. Special attention was given to its effects on blood pressure, because of reports that it reversed the normal pressor response of the patient to epinephrine and so increased the danger of hypotension. This reversal, though seen in laboratory animals, was not demonstrable in human subjects receiving the doses of chlorpromazine and epinephrine especially given for the purpose. The chlorpromazine did reduce the magnitude of the pressor response to epinephrine, especially in patients under spinal anesthesia. In those patients whose initial blood pressure was below 140 mm. Hg, the chlorpromazine premedication had little additional depressor effect when compared to standard premedication. Experience showed that the hypotension induced by chlorpromazine was not a handicap to patients receiving adequate oxygen, water, and electrolytes and that it was preferable to the state of compensated normotension that sometimes masks impending shock.