Effect on respiration of diazepam, chloropromazine and haloperidol in patients with chronic airways obstruction.

The effect on respiration of diazepam, haloperidol and chloropromazine in patients with chronic airways obstruction was studied on ten patients by the modified rebreathing method of ventilatory response to carbon-dioxide. The two parameters of the ventilatory response studied were: (a) the slope expressed as litres/minute/mmHg CO2 and (b) minute ventilation at a computed pCO2 57 mmHg (VE 57). A significant decrease in either of these parameters indicated respiratory depression. Following administration of 10 mg diazepam intramuscularly to ten patients a significant depression of respiration was observed in five patients. Administration of 50 mg chloropromazine intramuscularly to eight patients significantly depressed respiration of three patients. A significant depression of respiration was not observed in any of the ten patients given 5 mg haloperidol intramuscularly. These results indicate that the lack of significant respiratory depression from an intramuscular injection of 5 mg of haloperidol to patients with severe chronic airways obstruction makes it a safer drug, for the management of acute psychotic episodes in such patients, than 50 mg of chloropromazine or 10 mg of diazepam given intramuscularly.