Alterations in response to somatic pain associated with anaesthesia. VII. The effects of nine phenothiazine derivatives.

IN the original publication on chlorpromazine, Courvoisier and her associates (1953) reported that this phenothiazine potentiated the intensity and duration of action of analgesic drugs in animals. They did not, however, show that chlorpromazine itself possessed any analgesic action. Schneider (1954) also found that it increased the duration of morphine analgesia in mice. Kopera and Armitage (1954), on the other hand, were unable to demonstrate any potentiation of morphine analgesia by either chlorpromazine or promethazine. All these workers used the same species of animals in their studies, employed the same technique for the measurement of analgesia and injected the same dosage of chlorpromazine (10 mg/kg). More recently, Tripod and Gross (1957), using a similar experimental technique, found that chlorpromazine increased the duration of morphine-induced analgesia, and demonstrated that promazine had a similar action.