Cytotoxic effect of chlorpromazine and its interaction with radiation on a mouse fibrosarcoma

Chlorpromazine hydrochloride (CPZ) was shown to exhibit a definite cytotoxic effect on mice fibrosarcomas in vivo under both normal and acutely hypoxic conditions. Administration of the drug (20 or 40 mg/kg) before exposure to 20 Gy of x rays caused a greater delay in growth than in tumours irradiated without the drug; an equal amount of growth delay was found at both doses. The effect of the combined treatment was greater than the sum of the effects of the two treatments given individually. However, since an equal delay in tumour growth was caused by CPZ given before or after irradiation, the combined effect, although synergistic, could not be described as radiosensitization. (U.K.)