Antagonism of the respiratory effects of alfentanil and fentanyl by naloxone in the conscious rabbit.

The ability of naloxone to antagonize the respiratory effects of alfentanil, a new short-acting analgesic, was studied in the rabbit. The results were compared with naloxone antagonism of fentanyl. Minute volume and respiratory frequency, and pH, PCO2 and standard bicarbonate of arterialized venous blood were measured. Naloxone was more effective as an antagonist to alfentanil than as an antagonist to fentanyl.